Glossary of Technical Sound Terms

In the process of selecting the right sound equipment, it can be a daunting task to wade through all the jargon used to describe different features and functions. Below is a glossary of several common technical terms used in live sound and recording.

This list will help you when trying to understand differences between equipment and selecting what will fit your needs best.

Ambient Microphones: A Sensitive mic, usually a condenser type, used to pick up the entire ambient sound of the room.

Auxiliary (AUX) Send: An output from the mixing console comprising a mix of signals from channels and groups derived independently of the main stereo/group mixes. Commonly used for monitor, record, effects or sound enhancement sends.

Bus: A mix of a number of audio signals, feeding to a common output.

De-esser (DS): A sibilance controller. Sibilance is a situation in which consonants like S's and T's are unduly prominient in speaking or singing. The de-esser is a signal processor that passes a signal unaltered unless it encounters high signal levels in roughly the 6kHz to 8 kHz range, where sibilant sounds occur. It momentarily compresses the signal to lower the level of these frequencies.

Equalizer (EQ): A device that boosts or cuts selected bands of frequencies in the signal path.

Fader: A linear (slider) control providing level adjustment.

Feedback: The “howling” or “ringing” sound caused by bringing a microphone too close to a loudspeaker driven from its amplified signal.

Frequency response: The range and accuracy with which components in a sound system handle different frequencies. Measurement is in hertz or kilohertz (Hz to KHz). The range of response on the low end of a 1/3 octave equalizer typically runs from 20 Hz on the low end to 20,000 Hz (or 20 KHz) on the high end.

Gain: The variation in level of a signal. Proper gain structure within a sound system allows for maximum dynamic range and the minimum level of noise a system is capable of generating.

Headroom: The available signal range above the nominal level before distortion occurs. Headroom may be thought of as a safety margin that allows room for all those dynamic peaks that give impact to music.

Limiter: A device which clamps the level of an audio signal below a preset limit, to avoid the possibility of overloading other parts in the signal path. A limiter, if properly set, will prevent distortion, feedback, or a signal level that is too strong — and will be transparent in nature.

Nominal: A signal's “average” level. Output meters of a properly gain-structured mixing console will read zero when the program material is at nominal level.

Peak: The high point in signal level clipping, or distortion, begins.

PFL (Pre-Fade Listen): A function that allows an operator to monitor the pre-fade signal in a channel independently of the main mix.

Phantom Power: The +48V power supply available at the channel mic inputs, for condenser mics and active direct boxes.

Trim Control: Sets the amount of gain created by the microphone preamp. The trim control is a variable setting knob provided for balancing signal levels between mixer inputs for the wide variety of input devices plugged into a mixer. For example, a tape deck provides a stronger output than a microphone. The trim control level for a tape deck will be set much lower than for that of a microphone. Individually setting the trim controls for each device allows a sound system operator to set the input faders of a mixer at unity gain — the optimal setting for each input.

Unity Gain: When a gain-providing circuit is set for zero boost. Settings at unity gain typically ensure balanced signal levels and a hedge against feedback.