Audio Glossary A-I
This is the simple, no-frills version. An enhanced hyperGlossary, where many of the terms have images, expanded definitions, cross-referencing and additional explanatory sections, is available in the members only zone. You can try the hyperGlossary demo here.
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If you would like to suggest a term that does not appear here, or to suggest other improvements, email me. *A reminder about the spelling used on this site and in this glossary. |
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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.
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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
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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
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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.
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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.
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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.
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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.
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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).
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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.
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So if some words don't look quite right to you, relax. We're not dyslexic, we just use Standard Oxford Dictionary spelling, not Websters.
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