A/v Terms | Ercmanns Car Audio

Audio/Video Terms and Definitions

Audio

A

A-B Test: A test between two components. For example, a test between two different pre-amplifiers. For the test to be scientifically valid, the levels should be matched.
ABX Comparator: A device that randomly selects between two components being tested. The listener doesn't know which device is being listened to.
AC3: See Dolby Digital
Acoustic suspension: A sealed or closed box speaker enclosure.

AES/EBU: Balanced digital connection. For example, used to connect a CD transport to a DAC. The AES/EBU standard uses XLR type connectors.
Alignment: A class of enclosure parameters that provides optimum performance for a woofer with a given value of Q.
Alpha: Term used in sealed enclosure designs to mean the ratio of Vas to Vb, where Vb is the volume of the box you will build.
Alternating Current (AC): An electrical current that periodically changes in magnitude and direction.
Ambience: The acoustic characteristics of a space with regard to reverberation. A room with a lot of reverb is said to be "live"; one without much reverb is "dead."
Ampere (A): The unit of measurement for electrical current in coulombs per second. There is one ampere in a circuit that has one ohm resistance when one volt is applied to the circuit. See Ohms Law.
Amplifier (Amp): A device which increases signal level. Many types of amplifiers are used in audio systems. Amplifiers typically increase voltage, current or both.
Amplifier classes: Audio power amplifiers are classified primarily by the design of the output stage. Classification is based on the amount of time the output devices operate during each cycle of signal swing. Also defined in terms of output bias current, (the amount of current flowing in the output devices with no signal).
Attenuate: To reduce in level. Analog: Before digital, the way all sound was reproduced.
Aperiodic: Refers to a type of bass-cabinet loading. An aperiodic enclosure type usually features a very restrictive, (damped), port. The purpose of this restrictive port is not to extend bass response, but lower the Q of the system and reduce the impedance peak at resonance. Most restrictive ports are heavily stuffed with fiberglass, dacron or foam.

Audiophile: A person interested in sound reproduction. Or audio enthusiast.

B

Baffle: A surface used to mount a loudspeaker.

Balanced: Referring to wiring: Audio signals require two wires. In an unbalanced line the shield is one of those wires. In a balanced line, there are two wires plus the shield. For the system to be balanced requires balanced electronics and usually employs XLR connectors. Balanced lines are less apt to pick up external noise. This is usually not a factor in home audio, but is a factor in professional audio requiring hundreds or even thousands of feet of cabling. Many higher quality home audio cables terminated with RCA jacks are balanced designs using two conductors and a shield instead of one conductor plus shield.
Bandwidth: The total frequency range of any system. Usually specified as something like: 20-20,000Hz plus or minus 3 db.
Band-pass Enclosure: A multi-chambered ported system.
Band-pass filter: An electric circuit designed to pass only middle frequencies.
Bass Blockers: Commercial name for auto-sound first order high pass crossovers (non-polarized capacitors), generally used on midbass or dash speakers to keep them from trying to reproduce deep bass.
Bass Reflex: A type of loudspeaker that uses a port or duct to augment the low-frequency response. Opinions vary widely over the "best" type of bass cabinet, but much has to do with how well a given design, such as a bass reflex is implemented.
Beaming: A tendency of a loudspeaker to concentrate the sound in a narrow path instead of spreading it.
Bessel crossover: A type of crossover design characterized by having a linear or maximally flat phase response. Linear phase response results in constant time-delay (all frequencies within the passband are delayed the same amount). Consequently the value of linear phase is it reproduces a near-perfect step response with no overshoot or ringing. The downside of the Bessel is a slow roll-off rate. The same circuit complexity in a Butterworth response rolls off much faster.
Bi-amplify: The use of two amplifiers, one for the lows, one for the highs in a speaker system. Could be built into the speaker design or accomplished with the use of external amplifiers and electronic crossovers.
Bi-wiring: The use of two pairs of speaker wire from the same amplifier to separate bass and treble inputs on the speaker.

Blu-ray Disc: A Blu-ray Disc (also called BD) is a high-density optical disc format for the storage of digital media, including high-definition video. The name Blu-ray Disc™ is derived from the blue-violet laser which, because of its short wavelength (405 nm), allows substantially more data to be stored than a comparably sized DVD. A Blu-ray Disc can store approximately 5X as much data as a DVD which uses a red laser with a wavelength of 650 nm. A benchmark for the purpose of calculating duplication speeds, a Blu-ray Disc™ takes about 45 minutes to burn its 25 GB of data at a 2X speed. On average, a single-layer Blu-ray Disc™ can hold a High Definition feature of 135 minutes using MPEG-2, with room for an additional 2 hours of bonus material in standard definition quality. A dual layer disc will extend this number up to 3 hours in HD quality and 9 hours of SD bonus material.
BNC: A type of connection often used in instrumentation and sometimes in digital audio. BNC connectors sometimes are used for digital connections such as from a CD Transport to the input of a DAC.
Boomy: Listening term, refers to an excessive bass response that has a peak(s) in it.
Bright: Listening term. Usually refers to too much upper frequency energy.
Bridging: Combining both left and right stereo channels on an automotive amplifier into one higher powered mono channel. When an amplifier is bridged, the impedance that the amplifier actually "sees" is calculated based upon the output of both stereo channels. Here is a simple formula to help define this:

Bridged Mono Impedance = (Y / X)/2

Y = impedance of driver(s) (both drivers should be identical)

X = # of drivers in circuit

One 4 ohm sub in bridged mono is equal to hooking up two 2 ohm subs in stereo, one to each channel.
Butterworth crossover: A type of crossover circuit design having a maximally flat magnitude response, i.e., no amplitude ripple in the passband. This circuit is based upon Butterworth functions, also know as Butterworth polynomials.

C

Cabin gain: The low frequency boost normally obtained inside a vehicle interior when subs are properly mounted.
Capacitor: A device made up of two metallic plates separated by a dielectric (insulating material). Used to store electrical energy in the electrostatic field between the plates. It produces an impedance to an ac current.

Center Channel: In home theater, sound decoded from the stereo signal sent to a speaker mounted in front of the listener, specially designed to enhance voices and sound effects from a movie soundtrack. Used in car audio to help offset skewed stereo imaging due to seating positions in the automotive environment.
Channel Balance: In a stereo system, the level balance between left and right channels. Properly balanced, the image should be centered between the left-right speakers. In a home-theater system, refers to achieving correct balance between all the channels of the system.
Clipping: Refers to a type of distortion that occurs when an amplifier is driven into an overload condition. Usually the "clipped" waveform contains an excess of high-frequency energy. The sound becomes hard and edgy. Hard clipping is the most frequent cause of "burned out" tweeters. Even a low-powered amplifier or receiver driven into clipping can damage tweeters which would otherwise last virtually forever.
Class A, Class A-B etc.: Amplifying an audio signal means using AC or DC current to increase the amplitude from low output to high. Different classes of amplifiers accomplish this in unique ways. Consider a Class A amplifier: turning a vacuum tube "on" or "off" with AC increases the efficiency of the amplifier, but adds unwanted distortion to the output signal. Therefore a Class A amplifier is relatively inefficient.
Cms: Mechanical suspension compliance of a driver, consisting of the spider and surround.
Co-axial: A speaker type that utilizes a tweeter mounted at the center of a woofer cone. The idea being to have the sound source through the full frequency range become "coincident".
Coaxial Driver: a speaker composed of two individual voice coils and cones; used for reproduction of sounds in two segments of the sound spectrum. See also triaxial driver.
Coherence: Listening term. Refers to how well integrated the sound of the system is.
Coloration: Listening term. A visual analog. A "colored" sound characteristic adds something not in the original sound. The coloration may be euphonically pleasant, but it is not as accurate as the original signal.

Compact Disc (CD): A small (approx. 5") optical disc on which data such as music, text, or graphic images is digitally encoded.
Compliance: The relative stiffness of a speaker suspension, specified as Vas.
Compression: In audio, compression means to reduce the dynamic range of a signal. Compression may be intentional or one of the effects of a system that is driven to overload.
Crossover: A frequency divider. Crossovers are used in speakers to route the various frequency ranges to the appropriate drivers. Additionally, many crossovers contain various filters to stabilize the impedance load of the speaker and or shape the frequency response. Some crossovers contain levels controls to attenuate various parts of the signal.

A passive crossover uses capacitors, coils and resistors, usually at speaker level. A passive crossover is load dependent (the transition may not be very smooth or accurate if a different speaker is substituted for the one the crossover was designed for).

An active crossover is based on integrated circuits (ICs), discreet transistors or tubes. An active crossover is impedance buffered and gives a consistent and accurate transition regardless of load.
Crossover Slope: High and low pass filters used for speakers do not cut-off frequencies like brick walls. The rolloff occurs over a number of octaves. Common filter slopes for speakers are 1st through 4th order corresponding to 6db/oct to 24db/oct. For example, a 1st. order, 6db/oct high pass filter at 100hz will pass 6db less energy at 50Hz and 12db less energy at 25Hz. Within the common 1st through 4th filters there is an endless variety of types including Butterworth, Linkwitz-Riley, Bessel, Chebychev, etc. Salesmen and product literature will sometimes make claims of clear superiority for the filter used in the product they are trying to sell. Since the subject fills books, suffice it to say that there is no one best filter, it depends on application and intended outcome. Good designers use the filters required to get the optimum performance from the system.
Cross-talk: Unwanted breakthrough of one channel into another. Also refers to the distortion that occurs when some signal from a music source that you are not listening to leaks into the circuit of the source that you are listening to.
Current (I): The flow of electrical charge measured in amperes.

D

DAC: A Digital to Audio Converter. Converts a digital bitstream to an analog signal. Can be a separate "box" that connects between a CD Transport or CD Player and a pre-amplifier. Damping (Damping factor, etc.): Refers to the ability of an audio component to "stop" after the signal ends. For example, if a drum is struck with a mallet, the sound will reach a peak level and then decay in a certain amount of time to no sound. An audio component that allows the decay to drag on too long has poor damping, and less definition than it should. An audio component that is overdamped does not allow the initial energy to reach the full peak and cuts the decay short. "Boomy" or "muddy" sound is often the result of underdamped systems. "Dry" or "lifeless" sound may be the result of an overdamped system.
D'Appolito: Joe D'Appolito is credited with popularizing the MTM (Midrange-Tweeter-Midrange) type of speaker.

DBX: A noise-reduction system that works as a compander across the full frequency spectrum. This noise reduction system must be played back using the DBX system.

Decibel (dB): Named after Alexander Graham Bell. We perceive differences in volume level in a logarithmic manner. Our ears become less sensitive to sound as its intensity increases. Decibels are a logarithmic scale of relative loudness. A difference of approx. 1 dB is the minimum perceptible change in volume, 3 dB is a moderate change in volume, and about 10 dB is an apparent doubling of volume.

0 dB is the threshold of hearing, 130 dB is the threshold of pain.
Whisper: 15-25 dB
Quiet background: about 35 dB
Normal home or office background: 40-60 dB
Normal speaking voice: 65-70 dB
Orchestral climax: 105 dB
Live Rock music: 120 dB+
Jet aircraft: 140-180 dB

Diaphragm: The interface between the air and the electronic components which allows the conversion of sound to electrical signals and visa versa.
Diffraction: A change in the direction of a wave front that is caused by the wave moving past an obstacle.
Dipole: An open-back speaker that radiates sound equally front and rear. The front and rear waves are out of phase and cancellation will occur when the wavelengths are long enough to "wrap around". The answer is a large, wide baffle or to enclose the driver creating a monopole.
Direct Current (DC): Current that moves in only one direction.
Dispersion: The spreading of sound waves as they leave a source. The spreading of sound waves as they leave a source.

Diversity: A reception technique by which two antennas are utilized to eliminate dropouts that occur when multiple signals arrive at the receiver at different times. A dropout can either be the result of a weak signal, causing a hissing sound, or a lapse in the silencing circuitry, which results in a popping noise. A diversity system constantly monitors the antennas to see which is providing the stronger signal at any given moment so that the receiver can take the strongest signal. A True Diversity system goes one step further by using two separate receivers housed in a single unit. Whichever receiver produces the stronger signal is the one that is used.
Distortion: Anything that alters the musical signal. There are many forms of distortion, some of which are more audible than others. Distortion specs are often given for electronic equipment which are quite meaningless. As in all specifications, unless you have a thorough understanding of the whole situation, you will not be able to make conclusions about the sonic consequences.
DIY: Abbreviation for Do - It - Yourself. In audio, the most common DIY is building speakers but some hobbyists build everything from pre-amps to amplifiers to DACs.
Dolby: Used for an electronic device that reduces noise from recorded or broadcast sound.

Dolby Digital: Is a five-channel system consisting of left, center, right and left rear, right rear channels. All processing is done in the digital domain. Unlike Dolby Prologic in which the rear effects channels are frequency limited to approx. 100-7000Hz, Dolby Digital rear channels are specified to contain the full 20-20Khz frequency content. The AC3 standard also has a separate subwoofer channel for the lowest frequencies.
Dolby Digital EX Surround: Also referred to as Dolby Digital 6.1, adds a rear, center channel to the existing left, center, right and rear speakers. This format requires a 6.1 processor or receiver and DVDs that are 6.1 encoded.
Dolby Prologic: Is a four-channel system consisting of left, center, right and rear channel, (the single rear channel is usually played through two speakers).
Dome Tweeter: A high frequency speaker with a dome-shaped diaphragm.A high frequency speaker with a dome-shaped diaphragm.

Double (Dual) Voice Coil (DVC): A voice coil with two windings, generally used in woofers. Each voice coil can be connected to a stereo channel, or both voice coils can be wired in parallel or series to a single channel.

DTS: Digital Theater System. A multi-channel encoding/decoding system. Used in some movie theaters. Also now included in some home-theater processors. A competitor to Dolby Digital.

DSP: Digital Signal Processing. DSP can be used to create equalization, compression, etc. of a digital signal.

DVD: Digital Video Disc or Digital Versatile Disc. A relatively new standard that seeks to combine better-than-laser-disc quality video with better-than-CD quality audio in a disc the size of a CD. Requires special players. Seems to be a viable candidate to replace both Laser Discs and CDs, but the jury is still out.

Dynamic Headroom: The ability of an audio device to respond to musical peaks. For example, an amplifier may only be capable of a sustained 100 watts, but may be able to achieve peaks of 200 watts for the fraction of a second required for an intense, quick sound. In this example the dynamic headroom would equal 3 db.

Dynamic range: The range between the loudest and the softest sounds that are in a piece of music, or that can be reproduced by a piece of audio equipment without distortion (a ratio expressed in decibels). In speech, the range rarely exceeds 40 dB; in music, it is greatest in orchestral works, where the range may be as much as 75 dB.

E

EBP: Efficiency Bandwidth Product. A guide that helps a designer determine whether a driver is more suitable for a sealed or ported enclosure. EBP of less than 50 indicates the driver should be used in a sealed, 50 - 90 indicates flexible design options, over 90 indicates best for a ported enclosure. EBP = Fs / Qes
Efficiency rating: The loudspeaker parameter that gives the level of sound output when measured at a prescribed distance with a standard level of electrical energy fed into the speaker. The loudspeaker parameter that gives the level of sound output when measured at a prescribed distance with a standard level of electrical energy fed into the speaker.
Electronic Crossover: Uses active circuitry to send signals to appropriate drivers. More efficient than passive crossovers. Uses active circuitry to send signals to appropriate drivers. More efficient than passive crossovers.
Electrostatic Speaker: A speaker that radiates sound from a large diaphragm that is suspended between high-voltage grids.
Equalizer: Electronic set of filters used to boost or attenuate certain frequencies.
Euphonic: Pleasing. As a descriptive audio term, usually refers to a coloration or inaccuracy that non-the-less may be sonically pleasing.
Extension: How extended a range of frequencies the device can reproduce accurately. Bass extension refers to how low a frequency tone will the system reproduce, high-frequency extension refers to how high in frequency will the system play.

F

Farad: The basic unit of capacitance. A capacitor has a value of one farad when it can store one coulomb of charge with one volt across it.
Fb: The tuned frequency of a ported box.
Fc or Fcb: The system resonance frequency of a driver in a sealed box. The system resonance frequency of a driver in a sealed box.
Feedback: Audio feedback, aka the Larsen effect, occurs when a sound loop exists between an audio input (microphone or guitar pickup) and an audio output (loudspeaker). This means a signal is received by a microphone, amplified and passed out of a loudspeaker. If the microphone can then receive the sound from the loudspeaker, a looping effect will be created. If too much sound looping occurs, the signal will "run away" and quickly degrade into an oscillation at some frequency. The resulting sound is a "squeal", "howl" or a combination of both. While audio feedback is usually undesirable, musicians and bands such as Jimi Hendrix, Robert Ashley, The Beatles, The Who and Nirvana have employed it with much success. Desirable feedback can be created with FX equipment using a simple delay of about 50 milliseconds feedback into the mixing console. The fader controls the volume of the feedback.
Filter: An electrical circuit or mechanical device that removes or attenuates energy at certain frequencies. . An electrical circuit or mechanical device that removes or attenuates energy at certain frequencies. .
Flat Response: The faithful reproduction of an audio signal; specifically, the variations in output level of less than 1 dB above or below a median level over the audio spectrum.
F3: The roll-off frequency at which the driver's response is down -3dB from the level of it's midband response.
Foley Sound Effects: Pre-recorded sounds used to enhance the soundtrack with action sounds in the final mixing process, e.g. receding footsteps, falling rain, and opening doors. Jack Foley (1891-1967) pioneered the art of adding sound effects to movie soundtracks using mechanical devices like springs (comic effect), flapping cards (machine guns), and snapping celery (bones breaking). Nowadays, Foley sound effects use modern technology to gain some or all of the same results. But like the original mechanical sounds these are pre-recorded to enhance content in movies, as well as other media.
Fletcher-Munson curve: Our sensitivity to sound depends on its frequency and volume. Human ears are most sensitive to sounds in the midrange. At lower volume levels humans are less sensitive to sounds away from the midrange, bass and treble sounds "seem" reduced in intensity at lower listening levels.
Free Air Resonance: The natural resonant frequency of a driver when operating outside an enclosure.
Frequency: The range of human hearing is commonly given as 20-20,000Hz (20Hz-20kHz). One hertz (Hz) represents one cycle per second, 20Hz represents 20 cycles per second and so on. Lower numbers are lower frequencies
Frequency agile (agility): Frequency agile devices adaptively learn which frequencies to skip over to avoid interference.
Fs: The frequency of resonance for a driver in free air.
Full-range: A speaker designed to reproduce all or most of the sound spectrum.
Fundamental: The lowest frequency of a note in a complex wave form or chord.

G

Gain: To increase in level. The function of a volume control.
Golden Ratio: The ratio of depth, width, and height based on the Greek Golden Rectangle. Often applied to speaker boxes or listening room design. The Ratio: W = 1.0, Depth = 0.618W, Height = 1.618W. The ratio of depth, width, and height based on the Greek Golden Rectangle. Often applied to speaker boxes or listening room design. The Ratio: W = 1.0, Depth = 0.618W, Height = 1.618W.
Grain: Listening term. A sonic analog of the grain seen in photos. A sort of "grittiness" added to the sound.
Ground: Refers to a point of (usually) zero voltage, and can pertain to a power circuit or a signal circuit. In car audio, the single most important factor to avoid unwanted noise is finding and setting a good ground.

H

Haas effect: If sounds arrive from several sources, the ears and brain will identify only the nearest. In other words, if our ears receive similar sounds coming from various sources, the brain will latch onto the sound that arrives first. If the time difference is up to 50 milliseconds, the early arrival sound can dominate the later arrival sound, even if the later arrival is as much as 10 dB louder. The discovery of this effect is attributed to Halmut Haas in 1949.

Harmonics: Also called overtones, these are vibrations at frequencies that are multiples of the fundamental. Harmonics extend without limit beyond the audible range. They are characterized as even-order and odd-order harmonics. A second-order harmonic is two times the frequency of the fundamental; a third order is three times the fundamental; a fourth order is four times the fundamental; and so forth. Each even-order harmonic: second, fourth, sixth, etc.-is one octave or multiples of one octave higher than the fundamental; these even-order overtones are therefore musically related to the fundamental. Odd-order harmonics, on the other hand: third, fifth, seventh, and up-create a series of notes that are not related to any octave overtones and therefore may have an unpleasant sound. Audio systems that emphasize odd-order harmonics tend to have a harsh, hard quality.
HDCD: High-Definition Compact Disc. A proprietary system by Pacific Microsonics that requires special encoding during the recording process. Some observers report HDCD discs as having better sound. To gain the benefits requires having special HDCD in your CD player.
Headroom: The ability of an amp to go beyond its rated power for short durations in order to reproduce musical peaks without distortion. This capability is often dependent on the power supply used in the design. Also known as Dynamic Headroom.
Head Unit (HU): The in dash control center of a car audio system, usually consisting of an internal low powered amp, AM/FM receiver, and either a tape or CD player (or both).
Hearing Sensitivity: The human ear is less sensitive at low frequencies than in the midrange. Turn your volume knob down and notice how the bass seems to"disappear". To hear low bass requires an adequate SPL level. To hear 25Hz requires a much higher SPL level than to hear 250Hz. In the REAL world, low frequency sounds are reproduced by large objects; bass drums, string bass, concert grand pianos, etc. Listen to the exhaust rumble of a 454 cubic inch V8 engine vs. the whine of the little four banger. The growl of a lion vs. the meow of your favorite kitty. As frequency decreases we perceive more by feel than actual hearing and we lose our ability to hear exact pitch.
Hertz (Hz): A unit of measurement denoting frequency, originally measured as Cycles Per Second, (CPS): 20 Hz = 20 CPS. Kilohertz (kHz) are hertz measured in multiples of 1,000.
High-Pass Filter: A circuit that allows high frequencies to pass but rolls off the low frequencies. When adding a subwoofer it is often desirable to roll-off the low frequencies to the main amplifiers and speakers. This will allow the main speakers to play louder with less distortion. High-pass filters used at speaker level are usually not very effective unless properly designed for a specific main speaker (see impedance below).
Hiss: Audio noise that sounds like air escaping from a tire.
Home Theater: An audio system designed to reproduce the theater sound experience while viewing film at home. Minimally consisting of a Dolby Pro Logic® surround sound receiver, left and right front speakers, a center channel speaker, and two surround speakers. These plus optional subwoofer(s), surround speaker(s), and digital formats such as Dolby Digital® can enhance the viewing experience by drastically improving the sound quality of movie soundtracks.
Hum: Audio electronic noise that has a steady low frequency pitch.

I

Imaging: Listening term. A good stereo system can provide a stereo image that has width, depth and height. The best imaging systems will define a nearly holographic re-creation of the original sound.

Impedance: Impedance is a measure of electrical resistance specified in ohms. Speakers are commonly listed as 4 or 8 ohms but speakers are reactive devices and a nominal 8 ohm speaker might measure from below 4 ohms to 60 or more ohms over its frequency range. This varying impedance curve is different for each speaker model and makes it impossible to design a really effective "generic" speaker level high-pass filter. Active devices like amplifiers typically have an input impedance between about 10,000-100,000 ohms and the impedance is the same regardless of frequency.

Inductance (L): The capability of a coil to store energy in a magnetic field surrounding it. It produces an impedance to an ac current. Inductors are commonly used in audio as low pass crossovers.

Infinite Baffle: A baffle that completely isolates the back wave of a driver from the front without a standard enclosure

Intercom: (intercommunication device) an electronic two-way communication system with at least one microphone and loudspeaker at each station for localized use. Utilizing a variety of microphone/speaker units that connect either wirelessly or via cable to a central control panel, individuals can use intercoms for a number of purposes. Most commonly intercoms are found in control and command applications including (but not limited to) warehouses and construction sites; film studios and theaters; and military commands and search and rescue operations.

IR (Infrared): IR refers to the section of the electromagnetic spectrum located between the red of visible light and the microwave bands (750 nm to 1 mm). IR wavelengths are used in the same way as radio waves for wireless connections between transmitters and receivers in audio systems. See More.

Infrasonic (Subsonic) Filter: A filter designed to remove extremely low frequency (25Hz or lower) noise from the audio signal. Useful for Ported box designs.

Interconnects: Cables that are used to connect components at a low signal level. Examples include CD player to receiver, pre-amplifier to amplifier, etc. Most interconnects use a shielded construction to prevent interference. Most audio interconnects use RCA connections although balanced interconnects use XLR connections.

Isobarik Enclosure: A trade name for a compound enclosure.

Jitter: A tendency towards lack of synchronization caused by electrical changes. Technically the unexpected (and unwanted) phase shift of digital pulses over a transmission medium. A discrepancy between when a digital edge transition is supposed to occur and when it actually does occur - think of it as nervous digital, or maybe a digital analogy to wow and flutter.

Kevlar: Material developed by Dupont that is has an exceptional strength to weight ratio. Used extensively in bullet-proof vests, skis, sailboat hulls, etc. In audio, used in many variations for speaker cones.
Kilohertz (kHz): One thousand hertz.

Le: The inductance of a driver's voice coil, typically measured at 1 kHz in millihenries (mH).

Line Level: CD players, VCRs, Laserdisc Players etc., are connected in a system at line level, usually with shielded RCA type interconnects. Line level is before power amplification. In a system with separate pre-amp and power-amp the pre-amp output is line level. Many surround sound decoders and receivers have line level outputs as well.

Line-Source: A speaker device that is long and tall. Imagine a narrow dowel dropped flat onto the water's surface. The line-source has very limited vertical dispersion, but excellent horizontal dispersion.

Lobing: Any time more than one speaker device covers the same part of the frequency range there will be some unevenness in the output. (Picture the waves from one pebble dropped into a calm pool vs. two pebbles dropped several inches apart.) Lobing means that the primary radiation pattern(s) is at some angle above or below the centerline between the two drivers. Good crossover design takes this into account.

Low Frequency Extension: Manufacturers, writers and salespeople toss around all kinds of numbers and terminology that can be very confusing and misleading. "This $300 shoebox sized sub is flat to 20Hz". Right, in your dreams . . . How is that cheap, tiny box and driver going to reproduce a 56 foot wavelength with enough power to be heard? It will not to it. Good bass reproduction requires moving a lot of air and playback at realistic volumes. Remember the rule of needing to move four times the air to go down one octave. Example: You have a pair of good quality tower speakers with 10" woofers that produce good bass down to around 40Hz. The salesman is telling you that his little subwoofer with a single 10" woofer will extend your system down to 20Hz. If you've been paying attention, you know that his woofer will have to move eight times as much air as each of your 10" woofers, not likely. Adding that subwoofer to your system might give you more apparent bass energy, and in fact may help a little with movie special effects, but it is unlikely to extend bass response significantly.

Low-Pass Filter: A circuit that allows low frequencies to pass but rolls off the high frequencies. Most subwoofers have low-pass filters built in and many surround sound decoders have subwoofer outputs that have been low-pass filtered.

Loudness: Perceived volume. Loudness can be deceiving. For example, adding distortion will make a given volume level seem louder than it actually is.

Magnetic-Planar Speakers: A type of speaker that uses a flat diaphragm with a voice coil etched or bonded to it to radiate sound. If the magnets are both in front of and behind the diaphragm, it becomes a push-pull magnetic-planar.
Maximum power rating: A meaningless specification.
Microfarads (mF): A measurement of capacitance.
Midbass: Mid frequency bass, usually frequencies just above the sub-bass range, from around 100 - 400 Hz or so.
Midrange: A speaker, (driver), used to reproduce the middle range of frequencies. A midrange is combined with a woofer for low frequencies and a tweeter for high frequencies to form a complete, full-range system.
Millihenries (mH): A measurement of inductance.
Monopole: Any speaker that encloses the backwave of the speaker device even though part of this backwave may be released via. a port or duct. The primary radiation at most frequencies will be from the driver front. If the driver is not enclosed it becomes a dipole.
MOSFET: Metal Oxide Semiconductor Field Effect Transistors. Used in most modern, quality car audio amplifiers in the power supply (and sometimes in the output stage). MOSFET's run cooler than normal bipolar transistors, and have a faster switching speed.
Muddy: Listening term. A sound that is poorly defined, sloppy or vague. For example, a "muddy" bass is often boomy with all the notes tending to run together.
Muting: To greatly decrease the volume level. Many receivers and pre-amplifiers have a muting control which allows the volume level to be cut way down without changing the master volume control. Great for when the phone rings.

Nonlinearity: What goes into a system comes out changed by its passage through that system-in other words, distorted. The ideal of an audio component and an audio system is to be linear, or nondistorting, with the image on one side of the mirror identical to the image on the other side.

Octave: An octave is a doubling or halving of frequency. 20Hz-40Hz is often considered the bottom octave. Each octave you add on the bottom requires that your speakers move four times as much air!
Ohm: A unit of electrical resistance or impedance.
Ohm's Law: The basic law of electric circuits. It states that the current [I] in amperes in a circuit is equal to the voltage [E] in volts divided by the resistance [R] in ohms; thus, I = E/R.
Opaque Projector: Similar to an overhead projector, with the added unique feature of being able to display three dimensional objects, such as book covers, photographs, and single sheets of paper.
Out of Phase: When speakers are mounted in reverse polarity, i.e., one speaker is wired +/+ and -/- from the amp and the other is wired +/- and -/+. Bass response will be very thin due to cancellation.
Output: The sound level produced by a loudspeaker. The sound level produced by a loudspeaker.
Overload: A condition in which a system is given too high of an input level. A common cause of distortion or product failure.
Overtones: See Harmonics.

Passive Crossover: Uses inductors (coils) and capacitors to direct proper frequencies to appropriate drivers. These crossover systems can be simple (First Order = 1 component @ -6 dB/octave slope) to complex (Fourth Order = 4 components @ -24 dB/octave slope).
Passive Radiator: A device that looks just like an ordinary driver, except it has no magnet or voice coil. A passive radiator is usually a highly compliant device, with a similar cone material and surround found on regular active drivers. The radiator must usually be at least as large (or larger) than the driver it is aligned with. The passive radiator is tuned to Fb and used in place of a port.
PCM: Pulse Code Modulation. A means of digital encoding.
Pe: Driver's rated RMS power handling capability.
Peak: The maximum amplitude of a voltage or current.
Peak power rating: Power output an amplifier is capable of during short musical bursts. i.e. symbol crashes. This rating is really pointless without a specific number of measure.
Peak-to-Peak power rating: See above.
Phase Coherence: The relationship and timing of sounds that come from different drivers (subs, mids, tweets) mounted in different locations.
Phase Distortion: A type of audible distortion caused by time delay between various parts of the signal.
Planar Source: Most electrostatics and magnetic planars have a large surface area. Think of a wide board dropped flat onto the water surface. The sound can be extremely coherent, but the listening window is effectively limited to being directly on-axis of both the left and right planar speaker.
Point-Source: Most multi-unit loudspeakers try to approximate a point-source. Think of a pebble dropped into the water and the expanding wave pattern away from impact. Obviously it is difficult to integrate multiple point-sources into a truly coherent expanding wave. The best designs do quite well with careful driver engineering and crossover development.
Polarity: A speaker, for example, has a positive and a negative input terminal. Connecting a battery directly to the speaker will result in the diaphragm moving outward. If you reverse the battery leads, the diaphragm will move inward. Caution: Too high of a voltage battery will also burn out the speaker!
Ported Enclosure: A type of speaker enclosure that uses a duct or port to improve efficiency at low frequencies. Also known as a bass reflex enclosure.
Power (P): The time rate of doing work or the rate at which energy is used. One equation for Power:

P = Volts^2 / Impedance

Push-Pull Configuration: One driver is mounted normally, the second is mounted so that it faces into the enclosure, both sharing the same internal volume and wired out of phase with one another. Although electrically out of phase with one another, the drivers are acoustically in phase since they move in the same direction. This alignment theoretically reduces second order harmonic distortion. This configuration is also known as an Isobaric Design.
Push-pull: Most common type of amplification that amplifies the negative and positive sides of the waveform separately. Allows for much higher power output than single-ended.
Pre-amplifier: Or Pre-amp is a device that takes a source signal, such as from a turntable, tape-deck or CD player, and passes this signal on to a power-amplifier(s). The pre-amp may have a number of controls such as source selector switches, balance, volume and possibly tone-controls.

Q

Q or Quality Factor: Is a measure of damping. Modern home speaker systems have Q values ranging from < .5 to approx. 2.0. Q values < .7 have no peak in the response. Q values around .5 are considered to be optimally damped, having a Bessel response. A Q of 1.0 is a Butterworth response. The lower the Q value, the better the transient response of the system, (less or no ringing), but the tradeoff is a larger required box size and the response begins to rolloff at a higher frequency. Another way to consider it is that the lower the Q, the more gradual the rolloff but the rolloff begins at a higher frequency.

Radio-frequency interference (RFI): Radio-frequency sound waves can be caused by many sources including; shortwave radio equipment, household electrical line, computers and many other electronic devices. RFI sometimes interferes with audio signals, causing noise and other distortions.
RCA Connector: "Phono" plugs, used primarily as low-level connections between Phonographs/CD players/Tuners/Recievers/Amplifiers...etc...etc
Receiver: An audio component that combines a pre-amplifier, amplifier(s) and tuner in one chassis. A Dolby Prologic Receiver also contains a Dolby Prologic decoder for surround sound.
Resistance (Re): In electrical or electronic circuits, a characteristic of a material that opposes the flow of electrons. Speakers have resistance that opposes current.
Resonant frequency: Any system has a resonance at some particular frequency. At that frequency, even a slight amount of energy can cause the system to vibrate. A stretched piano string, when plucked, will vibrate for a while at a certain fundamental frequency. Plucked again, it will again vibrate at that same frequency. This is its natural or resonant frequency. While this is the basis of musical instruments, it is undesirable in music-reproducing instruments like audio equipment.

Reverberation: Reverberation (sometimes called reverb or " echo ") occurs when a sound persists after its source stops emitting it. Sometimes reverberation is intentional - as in sound "effects" which can be added to an audio source during a recording or a live presentation. At other times reverb can be unintentional or even a problem. Acoustical engineers spend significant effort trying to reduce reverb in large venues, such as cathedrals or opera houses. A far cry from the Greek myth of Echo, modern engineers can reduce reverb with new acoustically absorbent material, and/or add reverb to sound tracks with the touch of a button and sophisticated digital software.
Ribbon Speaker: A type of speaker that uses a pleated conductor suspended between magnets. Most true ribbons are tweeters only. Sometimes confused with magnetic-planar speakers.
RMS (root-mean-square): The square root of the mean of the sum of the squares. Commonly used as the effective value of measuring a sine wave's electrical power. A standard in amplifier measurements.
Roll-off (cut-off): The attenuation that occurs at the lower or upper frequency range of a driver, network, or system. The roll-off frequency is usually defined as the frequency where response is reduced by -3 dB.

Satellite: A satellite speaker is usually fairly small, and does not reproduce the lowest frequencies. Usually meant to be used with a woofer or subwoofer.
Sd: The effective piston area of a driver. The effective piston area of a driver.
Sealed enclosure: An air tight enclosure that completely isolates the back wave of the driver from the front. Very tight, defined sound (with Qtc = 0.707) with very good transient response and power handling.
Sensitivity: A measurement of how much power is required for a loudspeaker to achieve a certain output level. The general standard used is on-axis SPL (Sound Pressure Level) at 1 watt input, 1 meter distance.
Signal-to-noise (SN) Ratio: The range or distance between the noise floor (the noise level of the equipment itself) and the music signal.
Sine wave: The waveform of a pure alternating current or voltage. It deviates about a zero point to a positive value and a negative value. Audio signals are sine waves or combinations of sine waves. The waveform of a pure alternating current or voltage. It deviates about a zero point to a positive value and a negative value. Audio signals are sine waves or combinations of sine waves.
Single-ended: Type of amplification often, (but not always), using vacuum tubes. Typically low power output, low damping factor and relatively high distortion. Single-ended enthusiasts claim that the sound quality is more "real".
Sound Pressure Level (Spl): Given in decibels (DB) is an expression of loudness or volume. A 10db increase in SPL represents a doubling in volume. Live orchestral music reaches brief peaks in the 105db range and live rock easily goes over 120db.
Soundstage: A listening term the refers to the placement of a stereo image in a fashion that replicates the original performance. A realistic soundstage has proportional width, depth and height.
Sound Waves: Sound waves can be thought of like the waves in water. Frequency determines the length of the waves; amplitude or volume determines the height of the waves. At 20Hz, the wavelength is 56 feet long! These long waves give bass its penetrating ability, (why you can hear car boomers blocks away).
Speaker Level: Taken from the speaker terminals. This signal has already been amplified.
Spectral balance: Balance across the entire frequency spectrum of the audio range.
Spider: The flexible material that supports the former, voice coil, and inside portion of the cone within the speaker frame.
Standing wave: A buildup of sound level at a particular frequency that is dependent upon the dimensions of a resonant room, car interior, or enclosure. It occurs when the rate of energy loss equals the rate of energy input into the system. This is what you hear when you listen into a sea shell.
Stereo: From the Greek meaning solid. The purpose of stereo is not to give you separate right and left channels, but to provide the illusion of a three-dimensional, holographic image between the speakers.
Subwoofer: A speaker designed exclusively for low-frequency reproduction. A true subwoofer should be able to at least reach into the bottom octave (20-40Hz). There are many "subwoofers" on the market that would be more accurately termed "woofers".
Surround (suspension): The outer suspension of a speaker cone; holds the diaphragm in place but allows it to move when activated. Usually made of foam or rubber.
Surround Sound: Sound extracted from the stereo signal sent to smaller rear or side speakers used in a home theater.

Thiele/Small parameters: The numbers that specify the behavior of drivers, as defined and analyzed by two engineers, Neville Thiele and Richard Small.
THX: Refers to a series of specifications for surround sound systems. Professional THX is used in commercial movie theaters. Home THX specifications are not published and manufacturers must sign non-disclosure waivers before submitting their products for THX certification. Manufacturers that receive certification for their products must pay a royalty on units sold.
Timbre: The quality of a sound that distinguishes it from other sounds of the same pitch and volume. The distinctive tone of an instrument or a singing voice.
Timbral: Refers to the overall frequency balance of a system. In a perfect world, all systems would have complete tonal neutrality. With current technology, this ideal is approached but not met. Listening to many equally "good" speakers will reveal that some sound warmer than others, some sound brighter etc. In a surround sound system it is important that all speakers have a close timbral match for the highest degree of sonic realism.
Total harmonic distortion (THD): Refers to a device adding harmonics that were not in the original signal. For example: a device that is fed a 20Hz sine wave that is also putting out 40Hz, 80Hz etc. Not usually a factor in most modern electronics, but still a significant design problem in loudspeakers.
Transducer: A device that converts one form of energy to another. Playback transducers are the phono cartridge, which changes mechanical vibrations into electrical energy, and the loudspeakers, which change it back, from electrical energy coming from the amp to mechanical movement of the diaphragm, causing audible pressure changes in the air.
Transmission Line: Also referred to as a T-line. A type of bass cabinet in which the back wave follows a relatively long, usually damped path before being ported to the outside. T-lines are usually rather large and costly cabinets to manufacture. Opinions vary widely over the "best" type of bass cabinet, but much has to do with how well a given design, such as a transmission line is implemented.
Transient response: The ability of a component to respond quickly and accurately to transients. Transient response affects reproduction of the attack and decay characteristics of a sound.
Transparency: Listening term. An analog that can be best "pictured" in photography. The more "transparent" the sound, the clearer the auditory picture.
Transients: Instantaneous changes in dynamics, producing steep wave fronts.
Tri-wiring: The use of three pairs of speaker wire from the same amplifier to separate bass, midrange and treble inputs on the speakers.
Tuning Frequency: The helmholtz resonant frequency of a box. Also refers to the resonant frequency of other types of systems.
Tweeter: A speaker, (driver), used to reproduce the higher range of frequencies. To form a full-range system, a tweeter needs to be combined with a woofer, (2-way system), or a woofer and midrange, (3-way system).

UHF: A UHF (Ultra High Frequency) electronic device transmits and/or receives a signal in a specified band or range of radio frequencies specifically reserved by the FCC (Federal Communications Commission). See More.

Unity gain: A circuit with unity gain will not increase or decrease the volume level.

USB: USB (Universal Serial Bus) is a standardized serial computer interface that allows peripherals to communicate with a host computer or PA system using a USB cable. It improves plug-and-play capabilities by allowing devices to be connected and disconnected without rebooting the host (also known as hot swapping). USB provides power, from the host, to low-consumption devices such as personal media players, digital cameras, microphones, headsets, or any device with a USB port. Installing individual device drivers is not required. Recently, PA system manufacturers have been including built-in USB ports into their systems for additional media playing options.

Vas: The equivalent volume of compliance, which specifies a volume of air having the same compliance as the suspension system of a driver.
Vb: The total box volume, usually in cubic feet or liters. Used specifically in sealed and ported designs.
Vf: The front volume of a bandpass design. The front volume of a bandpass design.

VHF: A VHF (Very High Frequency) electronic device transmits and/or receives a signal in a specified band or range of radio frequencies specifically reserved by the FCC (Federal Communications Commission). See More.
Vr: The rear volume of a bandpass design.
Voice coil: The wire wound around the speaker former. The former is mechanically connected to the speaker cone and causes the cone to vibrate in response to the audio current in the voice coil.
Volt (E): The unit of measurement used to measure how much "pressure" is used to force electricity through a circuit.

Warmth: A listening term. The opposite of cool or cold. In terms of frequency, generally considered the range from approx. 150Hz-400Hz. A system with the "proper" warmth will sound natural within this range.
Watts or Wattage: Is the unit of power used to rate the output of audio amplifiers. For a wattage number to have meaning the distortion level and impedance must also be specified.
Wavelength: The distance the sound wave travels to complete one cycle. The distance between one peak or crest of a sine wave and the next corresponding peak or crest. The wavelength of any frequency may be found by dividing the speed of sound by the frequency. (Speed of sound at sea level is 331.4 meters/second or 1087.42 feet/second).
Woofer: A speaker, (driver), used for low-frequency reproduction. Usually larger and heavier than a midrange or tweeter.

X

XLR: A type of connector used for balanced lines. Used for microphones, balanced audio components and the AES/EBU digital connection.
Xmax: The maximum linear cone excursion of a driver, measured in inches or millimeters. Caution; this should be specified as linear excursion one way, but many manufacturers list the the total excursion both ways which falsely doubles the value!

Y-Adapter: Any type of connection that splits a signal into two parts. An example would be a connector with one male RCA jack on one end, and two female RCA jacks on the other end.

Zobel Filter: A series circuit consisting of a resistance and capacitance. This filter is placed in parallel with a speaker driver to flatten what would otherwise be a rising impedance with frequency.

Video

#'s

1080i: A high-definition video format that has 1080 lines of vertical resolution and uses interlacing. More info: 1080i

1080p: A high-definition video format that has 1080 lines of vertical resolution and uses progressive scanning. More info: 1080p

16x9: A widescreen aspect ratio that is 16 units wide by 9 units high. More info: Aspect Ratios

2:3 Pulldown: A method of converting 24fps film to video by repeating one film frame as three video fields, then repeating the next film frame as two video fields.

3D: Three-dimensional, or having appearance the appearance of three dimensional depth. 3D images can refer to stereoscopic images (one image for each eye) or computer-generated images based on three-dimensional modeling. More info: 3-D

3GP: A video format based on MPEG-4, used for mobile devices such as cellphones. More info: MPEG-4

4:1:1: A video compression ratio in which the chroma (colour) is sampled at one quarter the rate of luminance (brightness). More info: 4:1:1

4:2:2: A video compression ratio in which the chroma is sampled at one half the rate of luminance. More info: 4:2:2

4:4:4: A video compression ratio in which the chroma is sampled at the same rate as luminance. More info: 4:4:4

4x3: The traditional television aspect ratio, 4 units wide and 3 units high. This aspect ratio is slowly being replaced by 16x9. More info: Aspect Ratios

4x3 Safe: A method of shooting widescreen footage while still retaining a "safe area" that can be cropped and used for 4x3 aspect ratio. More info: Aspect Ratios

5.1 Audio: A surround sound system that provides five separate audio signals: Left, middle, right, rear left, rear right. An additional low frequency (LFE) channel is also provided.

720p: A high-definition video format that has 720 lines of vertical resolution and uses progressive scanning. More info: 720p

AC Adapter: A circuit which modifies an AC current, usually converting it to a DC current. More info: AC Adapter

A/D Converter: A circuit which converts a signal from analogue to digital form; the opposite of a D/A converter. More info: A/D Converter

Adobe: A software manufacturer based in San Jose, California, and traded on the Nasdaq National Market under the symbol ADBE. Adobe is a leading provider of media productivity software. More info: Adobe Tutorials, Adobe Premiere, Adobe Photoshop, Adobe ImageReady

AGC: Automatic Gain Control. A circuit which automatically adjusts the input gain of a device, in order to provide a safe and consistent signal level. AGCs can be handy features, but professional applications often require manual gain control for optimum results.

Aliasing: Distortion of an image file or sound recording due to insufficient sampling or poor filtering. Aliased images appear as jagged edges, aliased audio produces a buzz. More info: Anti-aliasing

Alpha Channel: A special channel in some digital images reserved for transparency information. More info: Alpha Channel

AM: Amplitude Modulation. A method of radio transmission which sends information as variations of the amplitude of a carrier wave.

Amperage: The amount of electrical current transferred from one component to another.

Ambient: The environmental conditions, e.g. surrounding light and sound. More info: Ambient Sound, Ambient Light

Amplifier: A device which increases signal amplitude. More info : Amplifiers

Amplify: To increase amplitude.

Amplitude: The strength or power of a wave signal. The "height" of a wave when viewed as a standard x vs y graph.

Analogue: Information stored or transmitted as a continuously variable signal (as opposed to digital, in which the analogue signal is represented as a series of discreet values). Analogue is often technically the more accurate representation of the original signal, but digital systems have numerous advantages which have tended to make them more popular (a classic example is vinyl records versus CDs).

Anamorphic Lens: A special type of wide-angle lens which stretches the width of the image but not the height, creating a widescreen aspect ratio. More info: Anamporhic

Antenna: A device which radiates and/or receives electromagnetic waves.

Aperture: Literally means "opening". The camera iris; the opening which lets light through the lens. By adjusting the size of the aperture, the amount of incoming light is controlled. The aperture size is measured in f-stops. More info: Video exposure/iris

ASF: Windows Media file format ending with the extension .asf. Used for delivering streaming video. More info: ASF files

Aspect Ratio: The ratio of width to height of an image. Can be expressed as a number, or a relationship between two numbers. For example, the standard television screen ratio is 4:3 (4 units wide by 3 units high) or 1.33 (the width is 1.33 times the height). The new "wide screen" television ratio is 16:9 (1.78), and many new video cameras have the option to record using this format. Theatrical film aspect ratios vary, but the most common is 18.5:10 (1.85). More Info: Aspect Ratios

ASX: Windows Media file format ending with the extension .asx. This is a metafile which works in conjunction with ASF files for delivering streaming video. More info: ASX files

Attenuator: A device used to reduce the gain of a signal. Effectively the opposite of an amplifier. More info: Attenuators

Audio: Sound. Specifically, the range of frequencies which are perceptible by the human ear. More info: Audio tutorials

Audio Dub: The process of adding audio to a video recording without disturbing the pictures. The original audio may be replaced, or kept and combined with the new audio.

Audio Insert: A feature of some video equipment which allows audio dubbing.

Automatic functions: Functions which are performed by equipment with little or no input from the operator. Auto-functions can be very useful, but tend to have serious limitations. As a general rule, it is desirable to be able to operate audio-visual equipment manually.

Auxiliary Channel: On audio mixers, a bus which has an independent feed from each individual channel. Each channel has a control to adjust the level being sent to the auxiliary master output, which in turn has a control to adjust the overall level at the output bus. The auxiliary channel may be a simple output (to feed a device such as a tape machine or monitor), or it may be a "loop". An auxiliary loop sends a signal from the auxiliary output bus to a signal processing device such as a reverb generator, then brings the output of that device into an "auxiliary return" bus (thus creating a loop from the desk to the device, back to the desk). This return bus will have a level control pot, which is used to mix the incoming signal into the mixer's master output bus. More info: Auxiliary Channel

AVI: "Audio Video Interleaved". A common digital video format, in which the audio is interleaved as "packets", into the video frames.

Backlight: A light which is positioned behind the subject. It's primary purpose is to make the subject stand out from the background by highlighting the subject's outline. More info: 3-point lighting

Backlight Correction (BLC): A feature of some cameras which increases the apparent brightness of the subject when lit from the rear.

Back Focus: The focus between the lens and the camera. Adjusted by a ring at the rear of the lens (the closest ring to the camera body). If the camera appears focused when zoomed in, but becomes out of focus when zoomed wide, the back focus needs adjusting. More info: How to focus and how to back-focus

Balanced Audio: An audio signal which consists of two "hot" signals plus the shield. The hot signals are inverted relative to each other as they travel along the balanced cable. They are re-inverted when entering an audio device — this has the effect of inverting any unwanted interference, thus eliminating it. More info: Balanced Audio

Bandpass Filter: A circuit which filters out all but a certain range of frequencies, ie. it allows a certain band of frequencies to pass.

Bandwidth: A range of frequencies.

Barn Doors: Metal projections attached to the front of a light, which can be positioned in various ways to control the dispersal of the light.

Batch Capture: The process of capturing multiple video clips automatically. A batch command is set up from the capture software which includes in and out points for each clip.

Baud: Unit of signal speed — the number of signal "bits" per second.

Best Boy: On a film set, the assistant to the Gaffer and Key Grip. More info: Best Boy

Beta (1): A group of video formats developed by Sony Corporation. Beta, Beta SP, Digital Beta and other variations are all professional television formats. Betamax is a failed consumer version, losing to VHS in the 1980's. More info: The Beta format, The VHS vs Beta War, Beta SP VT

Beta (2): A pre-release version of computer software. Often distributed widely without charge, in order to obtain feedback, identify bugs, and attract customers.

Binary: The "base two number system" which computers use to represent data. It uses only two digits: 0 and 1. Binary code represents information as a series of binary digits (bits). In the table below, binary numbers are shown with their decimal equivalents.

Decimal: 0 1 2 3 4 5 6 7 8 9 10

Binary: 0 1 10 11 100 101 110 111 1000 1001 1010

Bit: Binary digit. One piece of binary (digital) information. A description of one of two possible states, e.g. 0 or 1; off or on.

Bitmap: A series of digital image formats, which record colour information for each individual pixel. As a result, the quality is very high, as is the size of the file.

Biscuit: Square/rectangular metal part which screws to the bottom of the camera plate, and allows the plate to attach to the head. The biscuit comes as part of the head's package, whereas the plate comes with the camera. The biscuit is the "interface" between the two, and is designed to attach to any plate, and fit into a corresponding slot on the head. When the head's quick-release mechanism is activated, the biscuit, plate and camera are all released as one. More info: Setting up a camera tripod

Black balance: A camera function which gives a reference to true black. When auto-black balance is activated (by a switch, positioned with the white balance switch), the iris is automatically shut, and the camera adjusts itself to absolute black. More info: Black balance, White balance

Black burst: A composite video signal with no luminance information, but containing everything else present in a normal composite video signal.

Black noise: Usually refers to silence with occasional spikes of audio. Other definitions are also in use but this is the most common. More info: Black noise, Noise colors

Blonde: A term used to describe tungsten lights in the 2Kw range. More info: Blonde Lights

Blue noise: Random noise similar to white noise, except the power density increases 3 dB per octave as the frequency increases. More info: Blue noise, Noise colors

Bluetooth: A wireless data transfer system which allows devices to communicate with each other over short distances, e.g. phones, laptops, etc.

Blu-ray: A high-definition DVD format supported by a group of manufacturers led by Sony. More info: The Blu-ray Format, Blu-ray vs HD-DVD

BNC: A type of video connector common in television production equipment, used to transmit a composite video signal on a 75Ω cable. More info: BNC connectors

Bridge: Another term for A/D converter.

Broadband: A general term to describe an internet connection faster than 56K. Broadband usually means 512K or greater.

Brown noise: Random noise similar to white noise but with more energy at lower frequencies. More info: Brown noise, Noise colors

Bucket: A solid coloured horizontal bar across the bottom of a colour bar test pattern. The most commonly used bucket colour in PAL patterns is red, referred to as a "bucket of blood". More info: Colour bars & test patterns

Burn: The process of recording information to an optical disk (CD or DVD).

Bus: Pathway which a signal passes along. For example, the main output of an audio mixer is referred to as the master bus. More info: Bus

Buzz Track: A recording of ambient audio, i.e. the background sound of a scene. More info: Buzz Track, Ambient Audio

Byte: A group of eight binary (digital) bits.

C: A computer programming language, with variations C+ and C++. More info: C

Cable Television: A system of television progam delivery via cable networks.

Camcorder: A single unit consisting of a video camera and recording unit. More info: Camcorders

Candlepower: A measurement of light, generally that which is output from an electric lamp.

Cans: An informal term for headphones. More info: Headphones

Capture Card: A type of computer card with video and/or audio inputs which allows the computer to import an analogue signal and convert it to a digital file.

CCD or Charged Coupled Device: The image sensing device of video and television cameras -- the component which converts light from the lens into an electrical signal. Made up of pixels - the more pixels, the higher the resolution. CCDs are commonly referred to simply as "chips". They replaced previous tube technology in the 1980's. Larger CCDs can naturally accommodate more pixels, and therefore have higher resolutions. Common sizes are 1/3" (pro-sumer level), 1/2" and 2/3" (professional level). Consumer cameras generally have a single CCD which interprets all colours, whereas professional cameras have three CCDs -- one for each primary colour.

CCU: Camera Control Unit. More Info: CCU

CD Compact Disc. Optical storage device, capable of storing around 600-700MB of data.

Channel (1) : On audio mixers, the pathway along which each individual input travels before being mixed into the next stage (usually a sub-group or the master bus). Each channel will typically have an input socket where the source is physically plugged in, followed by a sequence of amplifiers / attenuators, equalisers, auxiliary channels, monitoring and other controls, and finally a slider to adjust the output level of the channel. More info: Audio Mixer Channels

Choker: A type of shot composition in video/film/photography that is closer than a standard closeup. A choker is typically framed on the subject's face from above the eyebrows to below the mouth. More Info: Shot types

Chroma Key: The process of replacing a particular colour in an image with a different image. The most common types of chroma keys are bluescreen and greenscreen. More Info: Chroma Key: Green Screen

Chrominance: Chroma, or colour. In composite video signals, the chrominance component is separated from the luminance component, and is carried on a sub-carrier wave.

Cinematographer: AKA Director of Photography, the person on a film production responsible for photography. More Info: Cinematographer

Cinematography: The art and science of movie photography, including both shooting technique and film development.

Clear Scan: A video camera function which allows the camera to alter it's scan rate to match that of a computer monitor. This reduces or eliminates the flicker effect of recording computer monitors.

Codec: Short for compressor/decompressor. A tool which is used to reduce the size of a digital file. Can be software, hardware or a combination of both.

Color Bars: A television test pattern, displaying vertical coloured stripes (bars). Used to calibrate vision equipment. There are numerous variations for different applications. More info: Test patterns

Colour Temperature: A standard of measuring the characteristics of light, measured in units called kelvins. More Info: Colour Temperature

Common Mode Signal: A signal which appears equally on both wires of a two wire line, usually unwanted noise. Common mode signals are eliminated with balanced audio cable. More info: Balanced audio

Component Video: A type of high-quality video signal which consists of separate signal components. Usually refers to Y/Pb/Pr, which includes one channel for luminance information and two for colour. More info: Component video, Video connectors

Composite Video: A type of video signal in which all components are recorded or transmitted as one signal. Commonly used with RCA and BNC connectors. More info: Composite video, RCA connectors, BNC connectors

Compression (1): A method of reducing the size of a digital file, whilst retaining acceptable quality. This may be desirable in order to save memory space or to speed up access time. In the case of digital video, large files must be processed very quickly, and compression is still essential for playback on consumer-level computers. Professional digital systems can work with uncompressed video. There are many compression techniques in common use, and digital video often uses various combinations of techniques. Compression can be divided into two types: "lossless" and "lossy". As the names imply, lossless techniques retain all of the original information in a more efficient form, whereas lossy techniques discard or approximate some information. With lossy compression, there is an art to finding a compromise between acceptable quality loss, and file size reduction.

Compression (2): Audio compression is a method of "evening out" the dynamic range of a signal. Compression is very useful when a signal is prone to occasional peaks, such as a vocalist who lets out the odd unexpected scream. The compressor will not affect the dynamic range until a certain user-definable level is reached (the "threshold") - at which point the level will be reduced according to a pre-determined ratio. For example, you could set the compressor to a threshold of 0db, and a compression ratio of 3:1. In this case, all signals below 0db will be unaffected, and all signals above 0db will be reduced by 3db to 1 (i.e. for every 1db input over 0db, 1/3db will be output). Other controls include the attack and decay time, as well as input and output levels. More info: Audio compression, How to use a compressor

Contrast Ratio: The difference in brightness between the brightest white and the darkest black within an image. More info: Contrast Ratio

Convergence: The degree to which the electron beams in a colour CRT are aligned as they scan the raster. More info: Convergence Test Patterns

CPU: Central Processing Unit., the "brain" of a computer.

Crab: Camera movement across, and parallel to, the scene.

Crossfade: A video and/or audio transition in which one shot/clip gradually fades into the next. AKA mix or dissolve. More info: The crossfade transition

Crossing the Line: A video transition in which the camera crosses an imaginary line drawn through the scene, resulting in a reversal of perspective for the viewer. More info: Crossing the Line

Crossover: An electrical network which divides an incoming audio signal into discreet ranges of frequencies, and outputs these ranges separately.

CRT: Cathode Ray Tube.

Cut (1): An instantaneous transition from one shot to the next. More info: The cut transition

Cut (2): A location director's instruction, calling for the camera and audio operators to cease recording and all action to halt.

D Series Tape Formats: A series of broadcast digital formats, designated D1, D2, etc. Dx is basically a replacement for 1-inch formats. D2 and D3 combine chrominance and luminance information, whereas D1 and D5 store them separately (and are therefore higher quality).

Dailies (1): Daily raw footage shot during the production of a motion picture (AKA rushes or daily rushes). More Info: Dailies

Dailies (2): Newspapers that are published every day (or 5/6 days per week).

DAT: Digital Audio Tape.

Data Rate: The amount of data which is transferred per second. In a video file, this means the amount of data the file must transfer to be viewed at normal speed. In relation to optical disks, this means the amount of data which can be read or written per second.

DC: Direct Current. The electrical current output by batteries, etc.

Decibel (dB): Logarithmic measurement of signal strength. 1/10 of a Bel.

Deep Focus: A cinematography technique which uses a large depth of field to keep the entire contents of the frame in focus. More Info: Camera Focus

Deliverables: The final products of the filmmaking process, used to create prints and other material for distribution. More Info: Deliverables

Depth of Field: The zone between the nearest and furthest points at which the camera can obtain a sharp focus. More Info: Depth of field

Depth Perception:The ability to recognize three-dimensional objects and understand their relative positions, orientation, etc.More Info: Depth perception

Device Control: A tool which allows you to control another device. For example, a window within a video editing package from which you can control a video camera.

Differential Amplification: Method of amplifying a signal, in which the output signal is a function of the difference between two input signals.

Digital: A signal which consists of a series of discreet values, as opposed to an analogue signal, which is made up of a continuous information stream.

Digital S: Professional digital tape format, introduced by JVC in the mid-1990s.

Digital Video Editing: Editing using digital video formats and computer software. Also known as non linear editing. More info: Digital video editing tutorial

Digital Zoom: A method of zooming which digitally crops and enlarges part of the image. This is not a true zoom and results in loss of quality. More info: Digital vs optical zoom

Dissolve: A video transition in which one shot dissolves (fades) into the next. AKA mix or crossfade. More info: The dissolve transition

DLP: Digital Light Processing. A television technology that uses a colored light beam which bounces across an array of hundreds of thousands of hinge-mounted microscopic mirrors attached to a single chip called a "micro mirror device".

Docutainment: From the words documentary and entertainment. A television programme which includes both news and entertainment content, or a blending of both. More info: Docutainment

Dolly: Any apparatus upon which a camera can be mounted, which can be moved around smoothly. More info: Dolly Shot, Dolly Grip

Dolly Zoom: A cinematography technique in which the camera moves closer or further from the subject while simultaneously adjusting the zoom angle to keep the subject the same size in the frame. More info: Dolly Zoom

Downstage: Toward the camera.

Dropout: Loss of part of a recorded video or audio signal, showing up as glitches on playback. Can be caused by damaged record heads, dirty tapes or heads, etc.

Driver: A piece of software which enables a piece of hardware to work with a computer. Usually supplied with the hardware, but can often be downloaded from the vendor's website.

Dry Run: Rehearsal, without recording or transmitting etc.

DTMF: Dual-Tone Multi-Frequency, better known as touch-tone. The standard system of signal tones used in telecommunications. More info: DTMF tones

Dutch Tilt: A camera shot which is deliberately tilted for artistic effect. More info: Dutch Tilt

DV: Digital Video. More info: The DV Format

DVCAM: Digital tape format from Sony. More info: The DVCAM Format

DVCPRO: Professional digital tape format from Panasonic, introduced in the mid-1990s.More info: The DVCPRO Format, DVCPRO50, DVCPRO HD, Illustrations : DVCPro VT Machine

DVD: (Digital Video Disc or Digital Versatile Disc). An optical disc format which provides sufficient storage space and access speeds to playback entire movies.More info: The DVD Format

DVD Authoring: The process of taking video footage, adding chapter stops, menus, and encoding the footage into MPEG files ready to be burned

DVD Burning: Taking the authored DVD files and physically writing them to a disk.

Dynamic Loudspeaker: Loudspeaker which uses conventional cone and dome drive elements.

Dynamic Microphone: A moving coil microphone, which doesn't require power. More info: Dynamic Microphones

Dynamic Range: The difference between the weakest and strongest points of a signal. More info: Dynamic Range

Earth Hum: An unwanted noise which has been induced into a video or audio signal by faulty earthing.

Edit: The process of assembling video clips, audio tracks, graphics and other source material into a presentable package. More info: Video editing tutorials

Edit Decision List (EDL): A list of all in points and out points for an editing task. Can be stored on a removable disc (e.g. floppy disc). This enables an edit to be constructed in one edit suite, then taken to another (better) suite to make the final version.

ENG: Electronic News Gathering. This term was introduced with the evolution of video cameras for shooting news in the field (as opposed to film cameras). It is still widely used to describe mobile news crews.

Exposure: The amount of light which is passed through the iris, and which the CCD or film is exposed to. More info: Video camera iris

Equalisation: The process of adjusting selected ranges of audio frequencies in order to correct or enhance the characteristics of a signal. More info: Audio Equalisation

Expansion: The process of increasing the dynamic range of a signal. More info: Audio Expansion

Fade: A transition to or from "nothing". In audio, to or from silence. In video, to or from a colour such as black. More info: Video fade

Field: In interlaced video, half a video frame. A field comprises every second horizontal line of the frame, making a total of 312.5 lines in PAL and SECAM, 262.5 lines in NTSC.

Film Noir: French for "black film" or "dark film". A term used describe a genre of film popular in America between 1940 and 1960. More info: Film Noir

Filter: A transparent or translucent optical element which alters the properties of light passing through a lens. More info: Camera filters

Flanging: In audio work, a type of phase-shifting effect which mixes the original signal with a varying, slightly delayed copy. Related info: Flanging Effect, Phasing Effect

Floating Point Color: Available in 32-bit color digital images, floating point space allows colors to be defined as brighter than pure white or darker than pure black. This has advantages in image processing techniques.

Flying Erase Head: In video recorders, an erase head which is mounted on the drum assembly. The erase head wipes any previous recordings as new ones are made. "Normal" erase heads are stationary, and mounted to the side of the head drum. Because of their close proximity to the record heads, flying erase heads provide cleaner edits. Related info: How to clean video heads

Floor Manager: In television production, the person in charge of the "floor", i.e. the area where the action takes place. Related info: Floor Manager

Focal Length: The distance from the centre of the lens to the camera CCD.

Focus: The process of adjusting the lens in order to obtain a sharp, clear picture.
adj. The degree to which an image is correctly focused. More info: Video camera focus

Forced Perspective: A photographic technique that creates an optical illusion by strategically arranging subjects and/or objects within the frame. The goal is to confuse the relationship between objects by making them appear closer, more distant, larger or smaller than they really are.

FPS: Frames Per Second. The number of video or film frames which are displayed each second.

Frame (1): The edges of a television / video / film image.

Frame (2): To compose a camera shot. More info: Camera framing, Common shot types

Frame (3): One complete video, television or film picture. In video and television, each frame is divided into two interlaced fields. PAL and SECAM systems deliver 25 frames per second, with 625 horizontal scan lines. NTSC delivers 30 fps with 525 lines.

Frame Rate: The number of video or film frames displayed each second (frames per second; fps). PAL frame rate is 25 fps, NTSC is 30 fps, film is 24 fps. Related info: Frame rates in video & film

Fresnel: A type of lens with concentric rings which focus the light. Pronounced fra-NELL.More info: The fresnel lens

Frequency Response: The sensitivity of a microphone (or other component) to various frequencies, i.e. the amount each frequency is boosted or attenuated. More info: Microphone Frequency Response

F-stop: Measurement of aperture. The higher the f-stop number, the smaller the aperture. More info: f-stops

F-type: A family of cable connectors, in which the centre (hot) pin is the centre wire of the cable itself.

Gaffer (1): Chief electrician on a film set. More info: Film Gaffer

Gaffer (2): Industrial-strength sticky tape, AKA duct tape.

Gain: The volume/amplification level of an audio or video signal.

Gauss: (pronounced "gows", abbreviation "G") Unit of magnetic induction.

Gel: (pronounced "jel") Semi-transparent heat-resistant material which is placed in front of a light source in order to modify it's colour temperature or other characteristics. Related info: Color Temperature

Geosynchronous: A satellite orbit in which the satellite remains in a fixed position above the Earth.

Graphic Equalizer: A type of audio equalizer which uses a graphical layout to represent the changes made to various frequencies. More info: Graphic Equalisers, Sound Equalization

Gray Card: A gray-coloured card which reflects a known, uniform amount of the light which falls upon it. Used as a reference to calibrate light meters and set exposure. More Info: Grayscale Chart, 18% Gray Card

Gray Noise: Random noise, similar to white noise, which has been filtered to make all frequencies appear equally loud to the human ear. More info: Gray noise, Noise colors

Green Noise: An unofficial term referring to the background ambient noise of the world. Can also mean the mid-frequencies of white noise. More info: Green noise, Noise colors

Green Room: A room located near the main stage in a studio or concert venue, where artists and guests wait before their appearance. More info: Green room

Green Screen: A film and video technique in which action is shot against a green screen, which is subsequently removed from the image and replaced with a different background. More info: Green Screen , Chroma Key

Grip: Person who is responsible for constructing and dismantling film sets, as well as laying down dolly tracks.

Halogen: Any of the four non-metallic elements fluorine, chlorine, bromine and iodine. Related info: Types of lighting

Head (1): The component which records an electrical signal onto magnetic tape, or reads a signal from tape into an electrical signal. Related info: Cleaning video heads

Head (2): The part which the camera is mounted on, atop a tripod, pedestal or other mounting. Allows the camera to pan and tilt. More info: Camera tripods

Headroom: The amount of space between the top of the subject's head and the top of the picture frame. More info: Camera framing

Hertz: Unit of frequency. One cycle per second.

HDBaseT: A digital connection used in home entertainment systems, designed to carry video, audio, ethernet, power and control data over a standard Cat5e/6 cable. More info: HDBaseT

HD DVD: A high-definition DVD format supported by a group of manufacturers led by Toshiba. More info: The HD DVD Format, HD-DVD vs Blu-ray

HDCP: High-bandwidth Digital Content Protection (AKA High-Definition Copyright Protection). A method of copy protection that prevents audio and video signals being copied across digital connections.

HDMI: High-Definition Multimedia Interface. A digital connection used in home entertainment systems. More info: HDMI connectors, HDMI cables

HDTV: High-Definition Television. More info: HDTV formats

Hi8: An analog video format introduced by Sony in 1989. More info: Hi8

HMI: Hydrargyrum Medium-Arc Iodide, a type of light which uses an arc lamp instead of an incandescent bulb to produce light. More info: HMI Lights

Hot (1): An image or part of an image which is excessively bright, i.e. overexposed. More info: Iris & Exposure

Hot (2): The wire in a cable, and the connecting pins, which carry the signal. Related info: Audio cables and connectors

Hyperfocal distance: In cinematography, the distance from the camera beyond which all objects can be brought into acceptable focus. Related info: Focus

Hz: Hertz. Cycles per second.

Impedance: A term in electronics which measures the amount of opposition a device has to an AC current (such as an audio signal). Technically speaking, it is the combined effect of capacitance, inductance, and resistance on a signal. More info: Microphone Impedance

Indeo: A digital video compression format.

Infra-red: Frequencies beyond the red end of the visible spectrum, i.e. frequencies with longer wavelengths than red light. Perceived by humans as heat. Commonly used for remote-control devices.

Infotainment: Television programming which blends information and entertainment. More info: Infotainment

In-point: The beginning point of an edit.

Interface: The point of contact between a tool and it's operator. A human/computer interface could be a keyboard or a mouse.

Interlace: The method of dividing a video frame into two fields; one made up of the odd-numbered horizontal lines, the other made up of even-numbered lines.

Internet: If you don't know what the Internet is, you're in trouble. Related info: Internet tutorials

Intranet: A "closed-circuit internet". A local network of computers linked in much the same way as the wider internet.

Iris: The circular opening (aperture) which controls the amount of light passing through to the camera's sensing element or film. More info: Video camera iris

Jack: A type of audio connector originally developed for telephone switchboards, and sometimes called a phone connector. Still in common use for musical and other audio equipment. More info: Jack Connectors

Jackfield: AKA Patch-panel. A board which accommodates connections between multiple sources. More info: Patch Panels

Jib: A revolvable camera mounting arm, which can be attached to a dolly or crane.

JPEG: Joint Photographic Experts Group. A standard for still-image compression. Related info: Using JPEG images on the Internet

Jump Cut: A video transition in which one shot appears to "jump" to another shot with very similar framing. Usually considered undesirable but can be used for dramatic effect. More info: Jump cuts

Jump the Shark: A colloquial term used mainly in the US, referring to a defining point in a TV or movie series that marks the beginning of a terminal decline in quality and/or popularity. It stems from the Happy Days episode in which the Fonz literally jumps a shark while waterskiing.More info: Jump cuts

Kelvin: A unit of temperature measurement. Colour is measured in kelvins. More info: Color temperature

Key Frame: In some forms of digital compression, uncompressed frames (key frames) are placed at regular intervals (eg. every 6th frame is uncompressed). Each subsequent frame exists as variations on the keyframe, until a new keyframe is introduced. The further apart the keyframes, the worse the overall picture quality.

Key Grip: Person in sharge of constructing and dismantling film sets and dolly tracks. Related info: Jobs in Film

LAN: Local Area Network. A network of computers connected via cables or a wireless system.

LANC: A connection developed by Sony, used to link remote-control units, edit decks, etc.

Lavalier Microphone (AKA lav, lapel or lap microphones.) A very small condenser mic designed to pick up speech from a single person. More Info: Lav Mics, Condenser Mics

Lens: A transparent structure made of glass or other material, with at least one curved surface, which causes the light rays passing through it to converge or diverge in a controlled fashion. More info: Lenses

Letterbox Format: In video and television, the practice of placing black bars at the top and bottom of the frame, in order to simulate a wide-screen format (as if the viewer were looking through the slot in a letterbox). More info: Letterbox format, Aspect ratios

Light: That section of the electromagnetic spectrum which is visible, ie. perceptable to the human eye. Specifically, white light contains the wavelengths from 400nm (nanometres) to 700nm. Light travels through a vacuum at approximately 300,000 km (186,000 miles) per second. More info: Lighting tutorials

Lighting, Three-Point: A standard lighting technique using three lights: The key, fill and back lights. More Info: 3 point lighting

Limiter: A device which limits the level of a signal to a specified threshold.More info: Audio Limiters

Loudspeaker: A transducer which converts electrical signals into sound waves.

Lower Third: The lower portion of a video frame which contains graphical information such as station ID, name/title key, etc. More Info: Lower Thirds

Luminance: Measure of brightness.

M, MII: Professional tape formats from Panasonic. The M format was based on VHS technology, and was introduced at about the same time as Beta (in the mid-1980's). The MII format was introduced a few years later to compete with Beta SP. MII uses a different sized cassette. More info: M, MII

MIDI: Musical Instrument Digital Interface. A standard of communication between musical instruments, controllers and computers.

Mid-Shot or MS: A camera framing term, half-way between a wide-shot and a close-up. A mid-shot of a person will show them from about the waist or chest up. More info: Mid-shot, Camera shots

MiniDV: A consumer-level digital video format. More info: The MiniDV Format

Mix (1): A video transition in which one shot gradually fades into the next. AKA crossfade or dissolve. More info: The mix transition

Mixer: A device which accepts multiple signal inputs (video or audio), processes them, and provides one or more outputs. The outputs are "mixes" of the input sources. More info: Audio mixers, Vision mixers

M-JPEG: See Motion-JPEG

Modulate: To "change". A signal can be transmitted via a carrier wave, by modulating the wave to represent the signal.

Monitor: A device used to view a video, graphic or text source, or to listen to an audio source. Video monitors use CRTs (cathode ray tubes), LCDs (liquid crystal displays), and other technologies. Audio monitors generally use cone drivers and horn divers, mounted in speaker cabinets.

Monocular: Related to having vision in only one eye, as opposed to binocular (stereo vision, with two eyes). More info: Depth Perception

Monopod: Camera stand, like a tripod with one leg. Has the advantage of being light and easily portable. More info: Monopods, tripods

Motion-JPEG: A digital video compression format based on the still image JPEG compression standard.

Morph: Computer-assisted process in which an image (or video) is gradually transformed (morphosed) into another.

MPEG: Moving Picture Coding Experts Group. A digital video compression standard. More info: The MPEG Format

WMA: Windows Media Audio file, a file format used for delivering digital audio. More info: WMA files

WMV: Windows Media Video file, a file format used for delivering digital video and audio. More info: WMV files

WMVHD: Windows Media Video file which features high-definition resolution. More info: WMVHD files

ND (Neutral Density) Filter: A filter which reduces the amount of light coming through the camera lens, without affecting it's colour temperature. Related Info: Colour Temperature

Noddies: Shots of the presenter / interviewer nodding, smiling, frowning etc. These can be shot after the interview and inserted during post-production. More info: Noddy shots

Non-Linear: Any method of video editing which doesn't require all shots to be assembled in a linear fashion. More info: Non-linear editing

NTSC: National Television Standards Commission. Video/broadcast standard used in the USA, Canada, Japan, Mexico, and other countries. Delivers 525 horizontal lines of resolution at 30 fps (frames per second).

OB: See Outside Broadcast.

Off-Line: Out of action, not currently useable.

Off-Line Edit: A "draft" edit, usually prepared in an off-line edit suite (at a lower cost), then taken to an on-line facility to make the final cut. Related info: Video Editing

On-Line (1): Operational.

On-Line (2): In multi-camera or multi-tape set-ups, the camera or videotape machine which is currently selected by the director. For example, in an outside broadcast, the on-line camera is the camera which is currently live.

On-Line Edit: The final version of an edit, prepared in a professional edit facility.

Optical: Of light/optics.

Optical Image Stabiliser (OIS): A system of stabilizing a camera image by constantly adjusting the optics.

Optical Zoom: A method of zooming which uses a telephoto lens, i.e. the zoom is provided by the optics rather than digital processing. Optical zoom is better than digital zoom More info: Digital vs optical zoom

Optics: Dealing with properties of light. Camera optics: The components which deal with light rays, before they are converted into electrical signals (i.e. the lens, etc).

Oscilloscope: Device which accepts an electrical input, and represents the variations of the input as a display on a CRT screen. More Info: Oscilloscope

Out-point: The end point of an edit.

Outside Broadcast: A radio or television program which is broadcast from location, rather than from a studio. More info: Outside Broadcast

PAL: Phase Alternate Line. Video/broadcast standard developed in Germany, and used primarily in Europe and Australasia. Delivers 625 lines at 25 fps (frames per second).

Pan (1): Horizontal camera movement.

Pan (2): The amount which a signal is divided between two pathways. For example, on an audio mixer, an input source can be panned across two stereo channels. Related info: Stereo

Pan and Scan: A method of converting widescreen film or video to 4x3 aspect ratio in order to be displayed on traditional television sets. The most important area of the frame is selected and the rest discarded. More info: Pan & scan, Aspect ratios

Pan Pot: Pan Potentiometer. A component which pans a signal across two pathways. Typically a knob or slider. The knob on a domestic stereo which pans between left and right speakers is a pan pot.

Parametric Equalizer: A type of audio equalizer which provides user-adjustable parameters such as frequency and bandwidth. More info: Parametric Equalisers, Sound Equalization

Patch Panel: AKA jackfield, a panel containing a series of connection points for electronic equipment. This allows equipment to be inter-connected in various configurations. More info: Patch Panel

Pattern Generator: A device capable of outputting various television test patterns. Used to test and calibrate vision equipment.

PCM: Pulse Code Modulation. A digital audio format.

Peak: The highest level of strength of a signal. If the "peak" or "clip" light on an audio mixer is activated, this means the respective bus (channel) is peaking at a dangerous level.

Pedestal (1): A movable mount for studio cameras. More info: Pedestal shot

Pedestal (2): The black level of a video signal.

Pepper Light: A small light, around 200w, used to light small spaces or to highlight certain features. More info: Pepper Lights

Persistence of Vision: A widely-accepted but scientifically unfounded theory which states that the human eye (and/or brain) always retains images for a fraction of a second. More info: Persistence of Vision

Phantom Power: A means of distributing a DC current through audio cables to provide power for microphones and other equipment. More info: Phantom power

Phasing: In audio work, an effect which utilizes phased wave interaction to create various sweeping sounds. Related info: Phasing Effect

Pink noise: Random noise, similar to white noise, that contains equal sound pressure level in each octave band.More info: Pink noise, Noise colors

Pixel: Picture Element.

Podcast: A portmanteau (fusion) of broadcasting and iPod. A system of syndicating multimedia content via the Internet for personal computers and portable devices. More info: Podcasting

Potentiometer or POT: Variable resistor. Potentiometers are used to adjust the level of a signal and are typically controlled by a knob or slider.

Power Amplifier: A device which accepts a relatively low level audio signal and boosts it to a level at which it can be output to a loudspeaker.

Power reset: Disconnecting power from a device (usually by turning it off), in order to purge all charges and reset the device to it's default settings.

PPM: Peak Program Meter. An audio level meter. More info: PPM Meters

Pre-Roll: The "lead-in" time at the beginning of a tape edit. When performing an edit, the tapes are rewound a few seconds, then played back before the edit begins. This ensures that the tapes are running at exactly the right speed.

Production: The process of creating a media product, or in some cases, the product itself.More info: The Production Process, Pre-production, Production, Post-production

PZM: Pressure Zone Microphone, AKA boundary effect microphone. This type of mic uses a flat surface to pick up the pressure waves bouncing of a "boundary" such as the floor, a table, wall, etc. These mics are often used in conference situations — the mic lies flat and unobtrusive in the middle of the table. More info: PZM mics

Quantization: The process of converting a continuous range of values into a finite range of discreet values. Used for various applications in digital image and audio production. More info: Quantization

Qubit: Short for quantum digit or quantum bit, the basic unit of a quantum computer, equivalent to the binary bit in traditional computers. Can be state 1 or 0 (pronounced ket 1 and ket 0), or a quantum superposition of the two — this allows vastly more possible states than the binary bit.

Quicktime: A digital media format originally developed for the Apple Computer range, but is now also available for other platforms. More info: The Quicktime format

RAM: Random Access Memory. A system of computer memory in which data can be retrieved in any order with equal speed.

RCA (1): The Radio Corporation of America, an American broadcast company.

RCA (2): A small non-locking connector. Typically used in home entertainment systems. More info: RCA connectors, Audio connections

Real Time: Anything which occurs without delay. A real-time effects proccessor will add effects instantly, without having to wait to render.

Red Head: A term loosely used to describe general-purpose tungsten lights in the 800w range. More info: Redhead Lights

Reflector Board: A specially-designed reflective surface which is used as a light source. More info: Reflector board

Resolution: The amount of detail in an image or signal. On a computer screen, the resolution is the number of pixels. In an analogue video signal, the resolution is the number of horizontal lines. In digital audio, the resolution is the number of samples per second.
"Colour resolution" refers to the colour depth of an image, ie. how many colours are present. More info: Resolution

Reverberation (Reverb): The amount of time it takes an emmitted sound to cease bouncing off objects such as walls. In audio work, adding a reverberation effect gives the sound more body and can make it sound as if it was recorded in a large room, hall, etc. More info: Audio Reverb

Reverse Cut: A video transition in which the camera "crosses the line", resulting in a reversal of perspective for the viewer. This is generally undesirable as it causes confusion. More info: Reverse Cuts

RGB: Red, Green and Blue. The primary colors of video.

Room tone: The background noise of a room. Almost but not quite silent. More info: Room Tone, Ambient Audio

Rule of Thirds: A technique in camera framing where the frame is divided into imaginary sections to create reference points. More info: The rule of thirds

Rushes: Daily raw footage shot during the production of a motion picture (AKA daily rushes or dailies). More Info: Rushes, Dailies

S-Video: A video signal that carries luminance (Y, brightness) and chrominance (C, colour) values as physically separate signals. Also known as Y/C video. Usually uses a small four-pin mini-DIN connector. First became popular during the S-VHS/Hi8 era.

Sample: A near-instantaneous recording of a signal, measured in thousandths of a second. Digital signals are constructed by sampling analogue signals thousands of times per second. Each of these individual samples are strung together to make a close approximation of the original signal.

Saturation: The level of colour in a vision signal or still image. A highly-saturated signal has very strong colours.

Scene: In film, television or stage, all the action/shots which take place at a certain time and location and comprise a segment of the program.

SCART: A type of multi-pin connector used in home entertainment systems. More info: SCART Connectors

Scissor Platform: AKA scissor lift, a mechanical work platform which can be raised and lowered. Sometimes used to elevate a camera position. More info: Scissor Platform

SECAM: Systeme Electronique Couleur Avec Memoire. Video standard used primarily by France and various Eastern Bloc countries. Provides 625 horizontal lines at 25 frames per second.

SEG: Special Effects Generator. A device used to create special video effects.

Servo: Remote control of camera functions such as zoom and focus, by means of a motor. Servo controls can be mounted an the lens housing, on the tripod/pedestal handles, or on a remote-control unit.

Setup: The black level of a video signal.

Shot: A continuous piece of video or film footage. Everything you get between pressing "record" and "stop". Related info: Camera shots

Signal Processing Device: Any device which takes a signal input, then modifies the signal before outputting it.

SLR: Single Lens Reflex, a popular type of still photography camera that uses a moveable mirror to synchronize the lens and viewfinder images.More info: SLR Cameras, Types of Camera

SMPTE: (Pronounced "simptee") Society of Motion Picture and Television Engineers. A group which has set various video standards.

Snow: Random patterns of black and white dots on a TV screen or vision monitor. Snow can be caused by an improperly tuned television (or very poor reception), an unrecorded video tape, or dirty VCR heads.

Solder: An alloy of tin and lead that melts at a relatively low temperature. Used for securing electrical connections between components and wires. More Info: How to Solder

Sound Reinforcement: The process of amplifying sound for the benefit of a live audience. More Info: Sound Reinforcement Systems

Speaker: See Loudspeaker

Stereo (1): Audio which is split into two channels.

Stereo (2): Duplicate images of the same scene, taken to simulate 3-D human vision. More info: See Stereo

Suspension of Disbelief: The semi-conscious act of allowing yourself to believe a fictitious premise for the sake of enjoying a story.

Tally Light: A small light on a video camera which turns on when recording is in progress. In multi-camera situations; a light on a camera, or in it's viewfinder, which turns on when the camera is switched on-line or live.

TBC: See Time Base Corrector.

Tele: (Prefix) Producing images or other results from a distance.

Telecast: Material broadcast by television.

Telecine: The process (or equipment used in the process) of transferring film to video and/or television. More Info: Transferring Film to Video

Telephoto: Telephotographic.

Telephotographic Lens: Magnifying lens, or combination of lenses. Related info: Video camera zoom

Teleprompter: Device which scrolls text on a screen, to provide cues for a television/video presenter.

Televise: To transmit by television.

Television: Literally means vision at a distance. The transmission, reception, and reproduction of moving pictures and audio. Refers to both the process in general, and the receiving appliance.

Tele-zoom: Longer zoom, producing greater magnification.

Test Pattern: Pattern of colours, lines and/or shapes designed to assist equipment calibration. More info: Video & television test patterns

Tilt: Vertical camera movement, i.e. adjusting the framing up and down.

Time Base Error: An error in the technical data of a video signal which causes picture distortion. More info: Time Base Errors

Time Base Corrector: A device which adjusts, improves and corrects defects in a video signal. Can be used to synchronise different vision sources before being mixed together, to avoid picture disturbances when cutting from one source to another. More info: Time Base Correctors, Timing video sources

Timecode: An indexing system that assigns a time value to individual frames of a film or video, or sections of an audio file. More info: Timecode

Tone (1): An audio test signal. Used to set signal levels, test signal quality, identify signal pathways, etc. More info: Audio Tone

Tone (2): In music, an interval of two semitones.

Tone (3): Quality of a person's voice, e.g. "The newsreader spoke in an authoritative tone".

Tone (4): Description of an attitude, mood, setting, etc. For example, "The tone of the movie was grim", or "The tone of the article was upbeat".

Transcoding: The process of converting one digital format to another, or re-encoding a digital file in order to change one or more parameters. More info: Transcoding

Transducer: A device which coverts energy from one form into another. For example, a microphone is a transducer which converts acoustical energy into electrical energy. Related info: Microphones

Transistor: A device used for switching or amplifying.

Transition: The way in which two video shots or audio clips are linked together; for example, instant cut, crossfade, wipe, etc. Related info: Video transitions

Transmitter: A device which converts video, audio and/or data signals into modulated radio frequency signals, and transmits them as radio waves.

Tripod: A three-legged stand for mounting equipment such as a camera, etc. More info: Video camera tripods

UER: Union Européenne de Radio-Télévision (www.ebu.ch).

UHF: Ultra High Frequency radio waves.

Ultrasonic: Audio frequencies above the upper limit of human hearing (approx 20,000 kHz).

Unbalanced Audio: An audio signal which consists of one "hot" signal plus the shield. This is common in home entertainment systems, as well as other systems with short audio cables. Unbalanced audio cables are prone to external interference, and are not prefered in professional situations. Related info: Balanced audio

UV: Ultra-violet light.

UV Filter: A filter which blocks out a certain percentage of ultra-violet light

Vacuum Tube: A multi-electrode valve which controls the flow of electrons in a vacuum from electrode to electrode.

VCR: Video Cassette Recorder. See also: VTR

Vector Image: A graphics image which exists as a series of geometric shapes, rather than as a series of values for each pixel. Has the advantage of being resizable without loss of quality.

Vectorscope: A device which graphically displays information about the chroma (colour) part of a vision signal. Used in conjunction with a waveform monitor (in fact, many devices are switchable between waveform and vectorscope modes). Related info: Calibrating video sources

VHF: Very High Frequency. This is a popular television broadcast band. It is lower than UHF (Ultra-High Frequency), and generally has a higher broadcast range.

VHS: Vertical Helical Scan. In the late1970s, VHS became known as Video Home System. VHS won the format war against Betamax, despite being technically inferior. More info: The VHS Format, The VHS vs Beta War, VHS-C

Video: There are many definitions of video, most of them rather loose. It essentially means any medium which displays moving images electronically (as opposed to mechanical film).

Video8: An analogue video format introduced by Sony in the 1980s. The first compact cassette format for camcorders. More info: Video8

Video Level: The strength of a video signal. Level is measured in volts/millivolts - the standard broadcast vision level is 1V peak-to-peak, of which 700mV comprises the picture information and 300mV comprises the timing and sync information. Related info: Calibrating video sources

Viewfinder: A component of video, television and film cameras. Available as EVF (Electronic Viewfinder) or OVF (Optical Viewfinder). An EVF has a small CRT which displays the camera output (or tape output). More info: Video camera viewfinder

Vision: The picture component of a video, television or film program (as opposed to the audio component).

Vision Control Operator: The person responsible for maintaining the technical quality of the vision signal(s). This may involve controlling some camera's functions remotely (such as iris, colour balance, etc.), as well as making adjustments to any vision source's technical characteristics (such as video level, timing, etc.). More info: Vision control (CCU)

Vision Mixer (1): A device which accepts multiple vision source inputs, manipulates them, and provides one or more vision outputs in real time.

Vision Mixer (2): A person who operates a vision mixer as described above. AKA vision switcher. More info: Vision switcher

VITC: (Pronounced "vitsee") Vertical Interval Time Code. A type of timecode used in some video tape formats.

Vocal: Of the human voice.

Volt: Unit of electromotive force. 1 volt, when applied to a 1 ohm conductor, produces a current of 1 ampere.

Voltage: Electromotive force, in volts.

Voltmeter: A device which measures voltage. One of the functions of a multimeter.

VOX (1): Voice operated switch.

VOX (2): Abbreviation for vocals.

Vox Pop: From the latin phrase vox populi, meaning "voice of the people". The vox pop is a technique used in many forms of media, to provide a "snapshot" of public opinion. Random subjects are asked to give their opinion on a particular topic, and these are presented to the viewer/reader as a reflection of popular opinion More info: Vox pops for video and television

VT: Video Tape. A magnetic storage medium for video. Related info: VT Operations

VTR: Video Tape Recorder. See also: VCR.

VU: Volume Unit, a unit to measure the volume of an audio signal. More info: VU Meters

Watt: Unit of power; equivalent to one joule per second. 1 watt (W) = 1 volt (V) x 1 amp (A)

Wattage: Amount of electrical power, in watts.

Wave: An oscillation which is propogated from place to place. Related info: Sound waves

Waveform: The shape (form) of a wave, or a representation of this form.

Waveform monitor: An oscilloscope specifically designed to display the waveforms of video signals. Used to monitor signal strength, sync timing, etc. See also: vectorscope

Wavelength: The distance between any point on a wave and the equivalent point on the next phase.

White balance: A camera function which gives a reference to "true white", in order for the camera to interpret all colours correctly. More info: Video camera white balance

White noise: Random noise that contains an equal amount of energy in all frequency bands. More info: White noise, Noise colors

Whizz-pan: A very fast camera pan, usually such that individual frames are severely blurred.

Wide screen: Generally refers to any video aspect ratio greater than 4:3. More info: Aspect ratio, Why go widescreen?

Wideshot (WS): A framing term, meaning a camera shot which shows the whole of the subject. More info: Wide shot, camera shot types

Wild sound: Another name for ambient audio, i.e. the background sound of a film scene. More info: Wild Sound, Ambient Audio

Wipe: A video transition in which parts of one shot are successively replaced by equivalent parts of the next shot. More info: Video wipes

Wow: Wavering of audio reproduction due to speed fluctuations.

Wrap: The end of shooting. This could refer to a single day's shoot or to the entire production phase.

XLR: A lockable connector, available with various numbers of pins (the most common being the 3-pin XLR). Often referred to as a "Cannon" after the original manufacturer of XLR connectors. More info: XLR connectors, Audio connectors

XML: Extensible Markup Language, a versatile markup language used in computer programming and web development. More info: XML

X-Y micing (X-Y pickup): A technique that uses two directional microphones aimed in an X or Y pattern to capture stereo sound.

XCU: Script designation for extreme close-up shot. AKA ECU. More info: ECU, Shot types

XLS: Script designation for extra long shot, AKA extreme long shot, extreme wide shot (EWS). More info: EWS, Shot types

Y: Luminance. The "brightness" of a signal.

Y/C: Luminance/chrominance. A video signal which consists of two signals: The luminance (brightness) and chrominance (colour). S-video connections use a Y/C signal.

Y-Lead: AKA "Split lead". A lead with one connector at one end, and two at the other. For example, a mono audio output could be split (using a y-lead) into two signals, to be plugged into the left and right inputs of another device.

Yagi: A type of highly directional antenna consisting of an array of straight elements in line with a dipole. The formal name is Yagi-Uda array.

YUV: A type of component video consisting of one luminance signal (Y) and two chrominance signals (U and V).

Zebra Stripes: A feature of professional cameras, which places diagonal lines across any over-exposed parts of the picture in the viewfinder. These stripes will not show on the output/recorded picture, they are only there as a guide for the camera operator. More info: Zebra Stripes, Video camera viewfinders

Zone System: A photographic system which divides light into ten tonal steps, from Zone 0 (absolute black) to Zone IX (absolute white). Zone V is medium gray, the same value found on an 18% gray card.

Zoom: Framing movement, in which the focal length of the zoom lens is altered to make the subject appear closer to, or further away from the camera. Note that this effect is similar, but not the same as moving the camera itself closer to or further away from the subject. More info: Video Camera Zoom

Zoom Lens: A lens with a moveable element, which is able to "zoom" between various focal lengths. This has the effect of making the subject appear closer to, or further away from the camera. More info: Video Camera Zoom

Zoom Microphone: A microphone on a video camera which adjusts it's pickup pattern to match the zoom lens, i.e. the mic becomes more directional as the lens zooms in. Related info: Microphones

Zoom Ratio: A number indicating the zoom range of a lens, arrived at by dividing the shortest focal length into the longest focal length. A 10 to 100 mm zoom has a zoom ratio of 10x. The number is sometimes stated as a ratio, e.g. 10:1.

**Not responsible for typagraphical errors.

ErcsAudio

ErcsAudio

Audio/Video Terms and Definitions

Audio

A

B

C

D

E

F

G

H

I

Video