Glossary :: Sound
ADAT: A digital audio signal providing 8 channels of audio over a single fibre optic cable.
AES: A professional digital audio signal, usually stereo and sent through an XLR connector.
AFL: (See also PFL) Stands for After-Fade Listen; a feature on sounds desks which allows you to listen to a particular output after the fader level through headphones.
Amplifier: This takes the low amplitude signal from the sound desk, and amplifies it so it can be sent to the speakers.
Auxiliary: Aux for short, an additional output on a sound desk into which any channel can be sent in addition to the main output. A "post fade" aux for a particular channel means the level at which the channel is sent to the aux depends on the level of the fader (usually the level at which it is also sent to the main output), and a "pre fade" aux allows the level sent to the aux to be independent from the level of the fader. Pre fade aux's are usually used for foldback and additional speakers, and pre fade is usually used to send to effects processors.
Balanced signal: A method of carrying audio signals that requires two connections (hot + and cold -) and ground. The cold connection is a phase reversed signal, and allows interference to be cancelled out. This type of signal is used for most equipment including mics, desks and amps, and uses either a 3 pin XLR connector or TRS jack connector.
Bender: A cable that has two different types of connector (such as jack to male XLR) or two XML connectors of the same gender.
Clipping: This happens when the level of a digital audio signal is too high, causing distortion. This can happen when an analogue signal is converted to digital, or when digital signals are gained or mixed together.
Compressor: A device inserted into the path of an audio signal (see insert) that automatically reduces the output level if the input level exceeds a set threshold. The harshness of the gain reduction (ratio) and time taken by the compressor to react can be adjusted. Used to even out the dynamic range of vocals and instruments.
Condenser Microphone: A type of microphone which requires an external power source as the signal is generated by adjusting an external source based on the movement of the diaphragm.
DI box: Stands for Direct Injection; a device that isolates and audio signal and allows conversion from and unbalanced to balanced signal. Requires a battery or phantom power and is usually used to connect electric guitars and keyboards to a desk
Dry: See Wet
DTI box: A specific make of device which is essentialy a transformer. This converts between balanced/unbalanced signals on phono, jack and XLR connectors, and is generally useful in many unthinkable situations...
Dynamic Microphone: A type of microphone which does not require power, generating its signal by the movement of a magnet within a coil, pretty much the inverse of a speaker.
Effects Processor: This is a device which can be connected to a sound desk and modify signals to provide effect such as reberb, echo, delay, chorus, pitch bend and distortion. Usually connected to an aux output form a desk with the modified signal sent to a new channel. Any channel on the desk requiring the effect would therefore be sent to the aux bus on a post fade setting.
Equaliser: (EQ for short) You find small equalisers on each channel in a sound desk, and also as a larger unit found between the sound desk and the amplifier in most systems. This is used to boost, or cut certain frequencies in an audio signal.
Feedback: This is when a sound level has been set too high, and the microphones on stage pick up the output from the loudspeakers. Any noise is then re-amplified, and you end up with an ear piercing noise!
Float mic: A microphone positioned a distance away from its source, used to pick up a large area such as a stage or choir. Usually a condensor mic due to the better performance with high frequencies at a distance.
Foldback: (not to be confused with feedback) This is a system in which speakers are set up pointing back to the performers so they can hear themselves sing/act. Famously, the Eurovision Song Contest is a good demonstration, where UK got 0 points, most likely because the foldback was set too low.... or, because Gemini were shit. You decide.
Gate: A device which is inserted into the path of an audio signal (see insert) and mutes the signal if its level is below a set threshold. The time taken to turn the gate on and off can also be set. Usually used on drums to mute the signal when the drum is not being played.
Ground Loop: Noise caused by multiple pieces of sound equipment having varying earth potentials, causing a current to flow and be induced on to signal cables. Often a pain to fix, but can be overcome by the use of ground lifts, DI boxes, or breaking the shield on connecting cables.
IEM: Stands for In Ear Monitor, a pair of headphones or ear pieces used as an alternative to a loudspeaker for foldback. May be wired or wireless.
Insert: A sound processing device, usually a gate or a compressor, which is inserted into a particular audio signal. Sound desks usually have insert jack sockets on each channel and some outputs, allowing the signal to be sent to an external device and back to the desk. This is usually a TRS jack connection which send and unbalanced signal out and back to the desk in one cable.
Jack: Another type of audio connector. Large jacks (1/4 inch) are typically used for line level connection into a sound desk (but serving a number of input and output purposes). They come in mono and stereo versions, Professionally, the stereo version is often use to carry mono, balanced audio.
Mini Jack: This is the standard audio connector you will find on your headphones, laptop and other small audio appliances.
Mixing desk: This is used to combine lots of audio sources together. They normally have multiple channels and a main output which is sent to the amplifier. The sound operator uses faders to alter the levels of different sources together.
Monitor: (see also foldback) a loudspeaker or headphones providing foldback to performers
Multicore: A type of cable that contains a large number of individual audio cables. Used to send multiple signals along a single cable, usually from the stage to a desk.
Noise Boys: Generic term for sound crew.
Outboard: Audio processing devices, such as gates, compressors and effects units, which are separate from the sound desk.
PFL: (See also AFL) Standing for Pre-Fade Listen, this is a feature of a sound desk that allows the operator to listen to what is coming in on one or more channels without putting it out over the PA.
Phantom: Refers to Phantom Power used to provide the power to condenser (and some other) microphones. The name refers to the fact that non-powered (e.g. dynamic) microphones will ignore the DC present on the audio lines, where as others will use it. Phantom power can be provided either by a battery or, most commonly, via XLR cable.
Post fade aux: See Auxiliary
Pre fade aux: See Auxiliary
RCA / Phono: This is a (domestic) mono audio connector, used normally to connect things like CD players and recording equipment to a sound desk.
Rifle mic: See shotgun mic
Shotgun mic: A type of condensor microphone with a very narrow pickup pattern. Good at isolating a sound from a distance by rejecting any sound not arriving directly in front. Also picks up some sound from directly behind, which means you need to be cautious about refletions if the mic is near a wall or ceiling.
Sidechain: An audio signal that can be sent to a compressor to trigger the compression. This is usually the same signal as the input signal being compressed; although this can be split and sent to an equaliser to trigger the compression when - for example - only the higher frequencies reach the threshold.
Sound Effects: These are usually small sound clips used during a show to add comic effect, or to replace for noises which cant be reproduced within the auditorium. Things such like telephone rings, doorbells, sirens, rain and thunder are good examples of sound effects.
SPDIF: A consumer digital audio signal. This is usually in stereo or 5.1 surround using phono connectors or fibre cables.
Speakon: This is the main type of connector which is used for connecting speakers. Alternatively you will find that large jacks, XLR or Terminal Posts are used.
Stagebox: A box containing a number of XML audio connectors, usually placed on stage to patch mics into a desk
TRS: (see also Jack) stands for Tip, Ring, Sleeve; a type of jack connector usually used to carry balanced or stereo signals
TS: (see also Jack) stands for Tip, Sleeve; a type of jack connector used to carry unbalanced signals
Unblanaced signal: An analogue audio signal that requires a single connection plus ground, and is much more susceptible to interference than balanced signals. Ususally produced by electric guitars, keyboards and headphone sockets, and usually uses TS jack or phono connections.
Wet: When applying an effect such as reverb with an effects processor, the "wetness" of the signal is how much of the signal is from the effects processor, and the "dryness" is how much of the original signal is kept. Sending signals to effects processors using post fade aux busses allow a combination of a wet and dry signal to be in the mix.
XLR: A type of cable connector: balanced audio signals usually use 3 pin XLR connectors and high quality audio cable. The term "XLR" is often used to refer to the entire sound cable. Not to be confused with DMX cables, used for lighting, which use 5 pin, and, sometimes, 3 pin XLR connectors. Audio signals do not sound nice through DMX cables!