Audio Glossary

 

A

AC: Alternating Current

Acoustic Coupling: The interaction between two or more speakers stacked together in a PA system which may produce a sound different to (and often better than) the sound produced by the individual speakers.

Acoustics: The area of study which deals with the behaviour of sound. Also the effect a given environment has on sound.

AIFF: Short for Audio Interchange File Format, a common format for storing and transmitting sampled sound, developed by Apple Computer and the standard audio format for Macintosh computers. Files are 8-bit mono or stereo and generally end with a .AIF or .IEF extension. Normal AIFF does not support data compression so files tend to be large, but another format called AIIF-Compressed (AIFF-C or AIFC) does support compression.

Amp: Abbreviation for ampere, the unit of electrical current. Also an abbreviation for amplifier.

Ampere: Unit of electrical current.

Amplifier: A device which increases or boosts the level of an input signal by increasing its amplitude.

Amplifier, Power: An amplifier without tone controls, usually with a higher power output than a line amplifier or pre-amp. Commonly used to drive loudspeakers.

Amplitude: The 'level' (perceived as 'volume') of an electrical or acoustic signal. Shown as the value of the vertical axis on a typical graph of a sound wave.

Analogue: Any quantity which varies continuously without distinct steps. For sound waves in air, this refers to the continuous variation in air pressure; for an audio signal, this refers to the continuous variation in current or voltage.

A&R: Abbreviation for 'Artists & Repertoire', and referring to the responsibility of an individual or company for management of both talent (Artists) and the material they write or perform (Repertoire).

Attenuate: To reduce the amplitude of an electrical signal usually by using a volume control, fader or 'pad'. Also to reduce sound levels acoustically through the use of acoustic absorbers, resonators or structural materials.

AU: Short for audio, a common format for sound files on UNIX machines. It is also the standard audio file format for the Java programming language. AU files generally end with a .au extension .

Audio Scrubbing: See 'Scrubbing'.

AVI: Short for Audio Video Interleave, the file format for Microsoft's Video for Windows standard.

 

 

B

Backline: Originally, the line or equipment, such as amplifiers, set up along the back of the stage. Stacks of amps/speakers were often used as much for the look they created as the sound they put out, dressing up the stage and giving it a more theatrical appearance. Loosely, backline is now taken to mean all the artist's stage equipment which is not part of the 'sound reinforcement'.

Balanced Line: A pair of ungrounded conductors ('hot' and 'cold') whose voltages are opposite in phase but equal in magnitude. At the destination end, the phase of the 'cold' is reversed thereby doubling the signal strength and cacelling any induced noise. Balanced lines therefore reduce interference from external sources like radio frequencies and light dimmers.

Bass: Lower register of pitch; also a stringed musical instrument designed to play low frequency sounds; also a voice lower in pitch than a baritone.

Biamplification: The use of separate amplifiers to power woofers and tweeters.

Board: Alternative name for mixing console or mixing desk.

Bump In / Out: The installation and removal of production equipment and services at a theatre venue.

Buss/Bus: A signal-carrying conductor or electrical pathway designed to carry multiple signals. e.g. a mixing console auxiliary bus may carry signals derived from several channels on that console

 

 

C

Canon/Cannon: Brand name of multipoint connector used for professional audio equipment - see XLR.

Capacitor Microphone: See Condenser microphone.

Cardioid: "Heart" shaped pattern exhibited by some microphones which reduces pick-up from the sides and back.

CD: Compact Disc

Channel: A single module of a professional audio console, lighting control console, power amplifier, lighting dimmer or multi-core control cable, designed to carry one signal only and keep it separate from signals in other channels.

Chops: Slang for musical technique.

Chord: A combination of two or more notes played together.

Circuit Breaker: An electrical switch that automatically breaks a circuit if the current through it is too high, then can be manually reset. Performs the same function as a fuse, without the need for replacement after activating.

Click Track: A regular sound, such as from a metronome, usually recorded on one track of a multitrack and used to indicate the required tempo for recording musicians.

Clipping: Audible distortion occurring when the peaks of an amplifier's output are flattened ('clipped'). When the input is too high, an amplifier has insufficient power to accurately reproduce the output waveform.

Compression (Audio): The process of reducing the dynamic range of a given analogue audio program by making the loud parts quieter and the quiet parts louder.

Compression (Data): The process of packing digital data, such as computer files, more efficiently for the purpose of storage or transmission. Commonly referred to as 'stuffing' or 'zipping' a file.

Compression (Audio/Video Files): A process of temporarily or permanently reducing audio data for more efficient storage or transmission. A temporary reduction in file size is called 'non-lossy' compression, and no information is lost. A permanent reduction in file size (such as with mp3 files) is called 'lossy' compression, and involves discarding (supposedly) unnecessary information which is irretrievably lost.

Compression Ratio: See Ratio

Compressor: A type of dynamic range processor which reduces the gain of audio signals which are over an adjustable 'threshold' level, therefore reducing the dynamic range. Generally allows the operator control over threshold, ratio, attack and release times. Both analogue and digital types are available.

Concert Pitch: A standard for the tuning of musical instruments, internationally agreed in 1960, in which the note A above middle C has a frequency of 440 Hz. The tuning used with middle 'A' corresponding to a frequency of 440Hz.

Condenser Microphone: A mic that depends on an external power supply or battery to electrostatically charge its condenser plates. Also called a 'Capacitor' microphone.

Conductor: Materials along which electrons will flow, making them suitable for use as connecting links in electrical circuits.

Conventional Current: The representation of current as flowing from positive to negative potential when describing the behaviour of electricity, despite the reality that the actual electrons constituting that flow move from negative to positive potentials!

Crossfade: A procedure in which one independent channel of information is raised as the other is lowered so that one smoothly replaces the other e.g. one audio track may 'crossfade' to another.

Crossover: An electronic circuit which splits an audio signal into different frequency bands for routing to different speakers optimised for that frequency.

Cue: 1. Foldback system used for recording studios. 2. The signal given to a performer to indicate the start of their performance.

Current: The flow of electrons along a conductor.

Cycles per second: See Hertz

 

 

D

DAT: Digital Audio Tape. Tape which stores data digitally rather than in traditional analogue format. Current DATs use 16-bit word size and 44.1 or 48kHz sample rate giving CD quality. However, shelf life is currently an unknown quantity.

DC: Direct Current

Decay: The way a signal reduces in level over time immediately after the signal stops.

Decibel or dB: A logarithm of a ratio used to indicate mathematically how a measured quantity compares to a standard reference quantity. One use, of many, is to represent Sound Pressure Levels (SPL) as numbers from 0dB (the softest sound that may be heard) to 120dB and beyond (the level at which sound is perceived as pain).

Delay: Signal processor which stores a signal for a short time before releasing it to the output. Combining the delayed and original sound allows for effects such as 'echo'. Multiple delay processors may produce 'time modulation' effects such as phasing, flanging and chorus.

Demo: A recording made for demonstration purposes for a record company, agent, venue owner, or to explore the potential of the song.

Desk: Mixing console.

DI: Direct Input box. A device used to match the level and impedance of sources such as guitar pickups to that expected by the microphone input of mixing consoles.

Digital: Represented by a numerical code. For sound, the conversion of an analogue waveform to a series of numbers representing the instantaneous amplitude for each sample taken, the storage of those numbers, and the eventual conversion back to analogue format for replay.

Distortion: Any difference, apart from level, between an original signal and one that has been processed. One cause may be the overloading of the input stage of an amplifier, but many other forms of distortion, such as harmonic distortion are common.

Drumfill: Foldback speakers placed at sides of drummer providing monitors coverage for performer.

Dry: Unprocessed sound.

Dub: To make a copy of a recording on another storage medium.

Dynamic Microphone: A microphone that converts sound into electrical energy by means of a moving coil located in a magnetic field.

Dynamic Range: The difference between the loudest and softest parts of a musical performance, usually measured in decibels.

Dynamics: When used in music, refers to the expression of a performance with varying degree of loudness and softness.

 

 

E

Earth: An electrical connection to the earth, which represents 0 volts or 'ground potential' by way of a metal or conductive rod.

Easter egg: A surprise usually coded into computer programs or web pages that is accessed by an undocumented keystroke combination or hidden link.

Echo: The combined effect of a sound and a delayed version of that same sound. A 'Slap-Back Echo' is the original sound plus a single repeat; "Multiple Echo" is the original sound plus several repeats with the same delay spacing.

Effect: A device which modifies sound creatively via processing.

Effects Rack: A cabinet containing outboard equipment. Designed to accommodate a number of standard width (19" or 48.3cm) rack-mountable devices. Pro-audio devices are always designed to have one of several standard heights in 'rack units' (RU), each RU being 1.75" or 4.44 cm.

EQ / Equalisation: The increase or decrease in level of certain portions of the audio frequency spectrum imposed by a device or acoustic environment.

Expander: A type of dynamic range processor which reduces the gain of audio signals which are under an adjustable 'threshold' level, therefore increasing the dynamic range. Generally allows the operator control over threshold, ratio, attack, release and 'hold' times. Both analogue and digital types are available.

 

 

F

Feedback: Sound produced by an instrument or microphone picking up and amplifying its own signal from a nearby loudspeaker. Also known as 'howlaround'.

Filter: A device that removes unwanted frequencies or noise from a signal.

FM Synthesis: Synthesiser technology which mimics different musical instruments according to built-in formulas. Generally considered to be inferior to Wave Table Synthesis.

FOH: Front-Of-House. Generally refers to the audience area, or that part of a venue not comprising the stage or backstage areas.

FOH Desk: Refers to audio or lighting control consoles at front-of-house, usually located towards rear of audience area.

FOH Engineer/s: Personnel responsible for operating audio and lighting systems, heard and seen by the audience as part of a performance.

Foldback (Live Sound): Also known as the monitor system, foldback comprises onstage speaker systems which enable the artist to hear his/her own performance, as well as other instruments and/or vocalists to varying degrees as controlled by the 'monitor engineer' or 'foldback engineer'.

Foldback (Studio): The system by which a performer in a studio may hear their performance through headphones. Also known as 'Cue'.

Frequency: the number of complete cycles that a sound wave goes through in each second. Unit used is Hertz, abbreviated to Hz, although some countries still use the older term 'cycles per second' (cps). Humans perceive frequency subjectively as pitch (eg: 440Hz = A).

Fuse: A safety device consisting of a low melting-point wire with a low melting pointwhich breaks an electrical circuit by heating up and melting ('fusing') if the current through it is too high.

 

 

G

Gaffer tape: Multi-purpose plasticised cloth tape often used to fasten leads on stage.

Gain: The amount by which an amplifier increases the power of a signal, indicated either in dB (e.g. Gain = +12dB), or as a multiplier (e.g. Gain = x4)

Gate: See 'Noise Gate'

GPO: General Purpose Outlet, or power point, capable of supplying normal mains power.

Gig: Slang for job, engagement of musicians to play and perform.

 

 

H

Hertz: (Abbreviation: Hz) The unit of frequency. Replaces 'cycles per second' and means the same.

High Pass Filter: A circuit that discriminates between high and low frequencies and allows only the high frequencies to pass.

Hook: A catchy part of a melody, riff or lyric which 'hooks' the listener's attention.

Howlaround: see Feedback

Hypercardioid: A narrower heart-shaped pick-up pattern than that of cardioid microphones.

HyperGlossary: A name made up by me to describe a glossary containing the usual text descriptions of terms, plus added hyperlinks to expanded definitions, examples, images and parallel universes ... (only joking about the universes).

 

 

I

Impedance: The measure of the total resistance to the current flow expressed in ohms (‡), in an alternating current circuit. It is an important characteristic of electrical devices (particularly speakers and microphones). Most speakers are rated at 4 or 8 ohms. Microphones are usually classified as being either high impedance (10,000 ohms or greater) or low impedance (50 ohms to 600 ohms).

Input Overload Distortion: Distortion caused by too great an input signal being sent to an amplifier or preamplifier. It is not affected by volume control settings and often occurs when mics are positioned too close to the sound source. This distortion is controllable through the use of an attenuator or pad.

Inverse Square Law: The law that states that in the absence of reflective surfaces, sound pressure (or light) falls off at a rate inverse to the square of the distance from its source. In other words, every time you double your distance from the sound source, the sound pressure level is reduced by a factor of 4, or 12 dB.

Insulator: Material preventing the flow of electrons, making it suitable for prevention of unwanted current flow in electrical circuits.

Integrated Amplifier: An amplifier containing two stages: a 'Pre-Amplifier' and a 'Power Amplifier'. Commonly used for domestic hi-fi applications.

Interface: A device which facilitates the linking of any two pieces of equipment or systems; or when used as a verb ('to interface'), the process of linking.

Jack: Female audio receptacle, or socket designed for male plug.

Jackfield: See Patchbay

JPEG: Short for Joint Photographic Experts Group, and pronounced jay-peg. JPEG is a lossy compression technique for color images. Although it can reduce files sizes to about 5% of their normal size, some detail is lost in the compression.

 

 

J

Jack: Female audio receptacle, or socket designed for male plug.

Jackfield: See Patchbay

JPEG: Short for Joint Photographic Experts Group, and pronounced jay-peg. JPEG is a lossy compression technique for color images. Although it can reduce files sizes to about 5% of their normal size, some detail is lost in the compression.

 

 

K

 

 

L

Leads: Signal-carrying cables used to connect various pieces of equipment.

Limiter: A compressor set up with a high ratio (in excess of 10:1) and used primarily to prevent a signal from exceeding a certain pre-set maximum level.

Line Level: A signal whose voltage is between approximately 0.310 volts and 10 volts across a load of 600 ohms or greater.

Load In / Out: The installation and removal of production equipment and services at music performance venues.

Loader/Lugger: Person providing labour for the above function whose responsibility is generally limited to lugging equipment between the production trucks and the stage or FOH positions. Their job generally does not include rigging or setting up the equipment, which is the responsibility of roadies.

Lossy Compression: A type of data compression which permanently discards data that humans supposedly "cannot hear" to create much smaller audio, video and image file sizes. When the file is decompressed by the recipient, this compression method replaces the data for the sections it removed with calculated values to restore the file. The decompressed file is similar but not identical to the original file.

Low Pass Filter: A circuit that discriminates between high and low frequencies and allows only the low frequencies to pass.

 

 

M

Mac: Apple Macintosh computer.

Master Fader: A fader which controls the overall level of one or more outputs simultaneously.

Metronome: Adjustable mechanical or electronic device which audibly indicates tempo. Some electronic versions may indicate beats per minute (bpm).

MIDI: Acronym for Musical Instrument Digital Interface, a standard adopted by the electronic music industry for controlling devices, such as synthesizers and sound cards, that produce music. At minimum, a MIDI representation of a sound includes values for the note's pitch, length, and volume, but can also include additional characteristics, such as attack and decay time.

MIDI files: A computer file format containing musical information and performance data.

Mic or Mike: Abbreviation of the word microphone.

Microphone: A device that converts sound pressure variations into electrical signals.

Minidisk: Recording and playback device using small disks similar to CDs to store audio using lossy data compression to reduce file size.

Mix: Blend of amplified or recorded sounds. In the recording studio, the process of combining and balancing the signals from two or more tracks of a multi-track recorder resulting in a final mix or 'master tape'.

Mixing console/desk: A signal-management device which receives, combines and balances signals, provides control of volume and tone, and allows routing of signals to selected destinations.

Modem: Short for Modulator -Demodulator, this device modulates data by converting it to audible tones that can be transmitted on a telephone wire, and demodulates received signals to get the data.

Monitor Desk: A mixing console located at the side of the stage which controls the on-stage sound balance through separate foldback speakers for the performers. The monitor mix, or foldback mix differs markedly from the FOH mix.

Monitors (Studio): Speakers used in the control room of a recording studio. Generally of two types: Main Monitors for overall sound, and Reference Monitors used to check sound quality through less capable speakers, such as might be found in domestic environments.

Monitors (Live Sound): Foldback speakers and associated amplifiers used for stage musicians.

MPEG: Short for Moving Picture Experts Group, and pronounced m-peg. The term also refers to the whole collection of digital compression standards and file formats developed by the group.

MP3, mp3: Is the file extension for MPEG, audio layer 3. Layer 3 is one of three coding schemes (layer 1, layer 2 and layer 3) for the compression of audio signals. Layer 3 uses perceptual audio coding and psychoacoustic compression to remove all superfluous information (that, in the opinion of the developers, the human ear doesn't hear anyway). It also adds an algorithm that increases the frequency resolution 18 times higher than that of layer 2. The result is mp3 encoding shrinks the original sound data from a CD by a factor of 12 without sacrificing sound quality.

Multicore: Audio or lighting cable containing many bundled leads allowing signal transmission along separate channels. Also known as 'Snake'.

Multimedia: The use of computers to present text, graphics, video, animation, and sound in an integrated way.

Multiple Echo: See 'Echo'.

Multi-tracking: The process of recording a multi-part performance on separate tracks at different times which allows the engineer to subsequently combine, balance and process those tracks during mixdown.

 

 

N

Noise Gate: A special type of expander with a very high ratio (usually about1:100), often used to eliminate low-level hiss, noise or leakage. Especially effective wherever there is a high level of ambient noise, such as around a drum kit.

Non-Lossy Compression: A form of data compression which seeks out chunks of data which are identical, replacing them with markers called keys. In this way, the file is reduced in size, and when it is decompressed by the recipient, the keys are replaced with the large chunks of data that were originally there (this is called Run Length Encoding). Using non-lossy compression, the uncompressed file is identical to the original file.

Nyquist's Theorem: This states that a sound must be sampled at at least twice its highest analog frequency in order to extract all of the information from the bandwidth and accurately represent the original acoustic energy. In practice, sampling at slightly more than twice the frequency will make up for imprecisions in filters and other components used for the conversion.

 

 

O

Ohm: The basic unit of the measurement of resistance. Symbol used is ‡ (Omega)

Ohm's Law: The law that defines the relationship between current (I), resistance (R) and voltage (V) in an electrical circuit as: Voltage equals Amperage times Resistance (V=IR).

Omnidirectional: Capable of picking-up sound equally from all directions (for microphones) or radiating sound equally in all directions (for speakers).

Outboard Equipment: Audio equipment which is not physically incorporated into the mixing console. If 'rack-mountable', it is generally located in an 'effects rack' and can include processors such as reverbs, delays, external equalisers, compressors, gates and enhancers.

Overdub: To record new tracks on a multitrack recording system in synchronisation with previously recorded tracks.

 

 

P

PA: Public Address system. A sound reinforcement system enabling live performances to be heard by the audience.

Pad: An electrical circuit used to attenuate or reduce the amplitude of an audio signal by a fixed amount, e.g a -15dB pad reduces the signal by a fixed 15 decibels.

Pan Pot: Short for panoramic potentiometer, this is a knob controlling a voltage divider that can send a signal to a combination of two busses, such as left and right. Always found on mixing consoles to set up (pan) a signal within the stereo field, it is also called a 'balance' control on domestic stereo amplifiers.

PCs: Personal computers. This term is generally used for IBM-compatible, Intel-based computers running DOS or Windows.

Patch Bay: A panel of jacks (female receptacles) hard-wired to all inputs, outputs and side-chains of outboard equipment, and all outputs and insert points of the mixing console. Often used in recording studios to enable rapid connection of any combination of equipment by the use of 'patch cords', or 'patch leads'.

Peak Power: A measure of amplifier power based on the amplitude rise above ground plane or 0 volts.

Peak-to-Peak Power: A measure of amplifier power based on the total amplitude between peak positive value and peak negative value. Generally this value is twice the peak value for a symmetrical waveform.

Phantom Power: Operating voltage (usually 48 Volts DC) supplied to a condenser mic by a mixer or external power source along normal mic leads.

Phase: The relationship of an audio signal or sound wave to a specific time reference.

Pick: See Plectrum

Pitch: The subjective sensation produced by various frequencies. The higher the frequency, the higher the perceived pitch; however, frequency is not linearly related to pitch. See also 'Concert Pitch'.

Plectrum: Triangular object generally made out of plastic used to strike the strings of a guitar.

Polarity: A condition with two states (+ve or -ve) and is usually defined in one of three ways: 1. Acoustical to electrical (microphone): Positive pressure at diaphragm produces positive voltage at pin 2 of XLR or at the tip of a 1/4-inch phone plug. 2. Electrical to acoustic: Positive voltage into the "plus" terminal of a speaker causes the speaker's diaphragm to move forward to produce positive pressure. 3. Electrical to electrical: Positive voltage into pin 2 of an XLR jack produces positive voltage at the output (pin 2 of an XLR plug, the tip of a 1/4-inch phone jack, or the red (plus) connector of a binding post (banana terminal).

Potentiometer (Pot): A variable resistor (rotary or linear) used to control volume, tone, or other functions of an electronic device.

Power: In electricity, power (P) is the product of the voltage (V) and the current (I). i.e. P=VI. The unit of power is the Watt.

Power Amplifier: An amplifier without tone controls, and with a higher power output than a line amplifier or pre-amp. Commonly used to drive loudspeakers.

Pre-amplifier/pre-amp: An electronic device used to match an input signal (such as that from a microphone or guitar pickup) to the input of a power amplifier. Often built in to mixing console channels as an initial stage, and generally has tone controls (EQ) to modify the signal.

Production Manager: Person responsible for co-ordination of audio, lighting and staging requirements, and crew, for any performance. Other responsibilities may include the scheduling of performances, physical placement of equipment and management of relevant health and safety matters.

Proximity Effect: An increase in the bass response of some mics as the distance between the mic and its sound source is decreased.

Punter: Slang for general or common audience.

 

 

Q

Q: Referring to the bandwidth of one band of a parametric equaliser, Q is calculated by dividing the centre frequency in Hz by the width of the boost or cut zone +3dB or -3dB above or below 0dB. For example, a gentle boost centred at 1000Hz which extends from 750Hz to 1250Hz measured 3dB above flat has a Q of 1000/500 = 2. By comparison, a deep notch centred at 1000Hz which extends from 995Hz to 1005Hz measured -3dB above flat has a Q of 1000/10 = 100.

Quality: See Timbre

QuickTime: A video and animation system developed by Apple Computer and built into the Macintosh operating system. It is used by most Mac applications that include video or animation. PCs can also run files in QuickTime format, but they require a special QuickTime driver. QuickTime supports most encoding formats, including Cinepak, JPEG, and MPEG. QuickTime is competing with a number of other standards, including AVI and ActiveMovie.

 

 

R

Rack-mountable: Describes outboard equipment designed to be mounted in a standard 19" EIA 'Effects Rack'.

Ratio: One of the parameters which can be varied on dynamic range processors such as compressors and expanders. It represents the compression or expansion ratio between input and output levels. A compressor with a 2:1 ratio would reduce the output gain to half of the input value above the threshold. An expander with a 1:80 ratio would reduce the output gain to 1/80th of the input value below the threshold.

RealAudio: The de facto standard for streaming audio data over the World Wide Web.

Recording: Capture and storage of sound for subsequent reproduction.

Reference monitors: See Monitors (Studio)

Repertoire: Compositions and lyrics; musical works.

Reverb: Abbreviation for reverberation, a complex blend of multiple interacting reflections within an enclosed space which combines with the direct sound from a source and defines the character of the sound in a room or hall. It is also used for a signal processor which can generate an approximation of natural reverb. (Caution: do not confuse with 'Echo' - a different effect altogether.)

Rhythm section: Section of the band which is responsible for laying down the beat, usually consisting of the drummer and bass player.

 

S
Saturation (Tape): The distortion caused by magnetic recording media being unable to store as much high frequency information as low frequency information.
Scrubbing: The process of moving within an audio file or tape to audibly locate a particular section. The term originally comes from the days of reel-to-reel players, when rocking a reel would give the impression of scrubbing tape across the head. Many audio scrub tools today allow the user to drag a cursor across the wave form to audition different sections of the audio file.
Sibilance: The distortion of sibilants by recording and reinforcement systems incapable of handling the high frequencies present in such sounds. See also "Saturation".
Sibilants: High frequency sounds in speech, such as "S", "F" & "T".
Sidefill: Foldback speakers placed at sides of stage providing general coverage for performers when monitor wedges are insufficient. See also'drumfill'.
Signal processors: Electronic devices which alter sound either to achieve a particular effect or to solve a problem with that sound (e.g. delays, compressors, reverbs, noise gates, equalisers).
Slap-Back Echo: See 'Echo'
Snake: See Multicore
Sonority: See Timbre
Sound Check; Soundcheck: The process of establishing the appropriate balance between the various instruments and vocals for both the FOH and monitor system prior to performing. Usually carried out by the engineer having the band play through several songs at the venue after the 'Room EQ' but before the gig.
Sound engineer: Person responsible for sound production.
Sound reinforcement: The use of amplification to project and reinforce sound for an audience. Speakers: Devices that convert electrical signals into variations in sound pressure.
Stack: A group or cluster of loudspeakers placed in close proximity to one another so they function more as a single unit due to acoustic coupling and other factors. Examples: PA stack; Marshall Stack.
Stage Box: A junction box at the stage end of a multicore equipped with female XLR connectors used for microphone signals destined for a mixing console at the other end. May also contain several male XLR connectors for signals sent back up the multicore from the console.
Streaming: A technique for transferring data such that it can be processed as a steady and continuous stream. Streaming technologies are often used on the Internet because most users do not have fast enough access to download large multimedia files quickly, so the client browser or plug-in can start displaying the data before the entire file has been transmitted.


T
Tablature or TAB: Notation commonly used by guitarists which indicates fingerboard position by numbers, symbols and diagrams.
Three Phase: A five-pin power supply system consisting of 3 legs/phases of active power with one earth and one neutral.
Timbre: The combination of harmonic frequencies in voices or instruments which give them their characteristic quality. Synonyms: 'Quality', 'Sonority', 'Tone Colour'.
Tone Colour: See Timbre
Transducer: A device designed to convert one form of energy into another. An example of a transducer that converts acoustic sound energy to electrical energy is a microphone; examples of a transducer that convert electrical energy to acoustic sound energy are speakers and headphones.
Tremolo: 1. A fluctuation of amplitude applied to a sound of constant frequency. Often incorrectly used, as in 'tremolo arm' on a guitar which actually produces vibrato. 2. For stringed instruments such as a mandolin, fast up and down strokes of equal strength of the plectrum or index finger on the strings.
Tremolo arm: a lever which alters string tension on an electric guitar, used to produce a tremolo or vibrato-like effect.
Truss: Section of steel or aluminium box, or triangularly-braced metal work used for suspending lighting or audio equipment.
Tuning: Adjustment of pitch of musical instruments to correct values.
Tuner: Electronic device used to tune acoustic or electronic instruments to standard pitch.


V
VCA (Voltage Controlled Amplifier): An amplifier whose output is controlled by varying its voltage rather than by direct resistance (as with a potentiometer).
VCO (Voltage Controlled Oscillator): An oscillator whose frequency output is controlled by varying its voltage rather than with a potentiometer.
VCF (Voltage Controlled Filter): An audio filter whose effective frequency band is controlled by varying its voltage rather than with a potentiometer.
Vibrato: Expressive effect which producers a fluctuation of pitch. A rapid, slight variation in pitch in singing or playing some musical instruments, producing a stronger or richer tone. It is often used as an expressive device.
Volume: Loudness of sound; a subjective sensation dependent on the amplitude of a sound wave or electrical signal, but not linearly related to it.


W
WAV: The format for sound files developed jointly by Microsoft and IBM, and built into Windows 95 which made it the de facto standard for sound on PCs. WAV sound files end with a.wav extension and can be played by nearly all Windows applications that support sound.
Waveform: A graphical representation of a signal as a plot of amplitude versus time, i.e. the shape of a wave.
Wave Table Synthesis: A technique for generating sounds from digital signals. Wave table synthesis stores digital samples of sound from various instruments, which can then be combined, edited, and enhanced to reproduce sound defined by a digital input signal. Wave table synthesis reproduces the sound of musical instruments better than Frequency Modulation (FM) synthesis.
Wedge: Foldback speaker placed on the floor at the feet of stage vocalists to deliver the monitor mix for performers.


X
XLR: Multipoint plug used for professional audio equipment