A separate room or enclosure, often called a 'Booth' designed to provide acoustic isolation from external noise. Often used alongside a studio's main live room to record vocals or drums, for example, without spill from other instruments.

Interrupt Request. Part of the operating system of a computer that allows a connected device to request attention from the processor in order to transfer data to it or from it.

Inches Per Second. Used to describe tape speed. Also the Institute of Professional Sound (www.ips.org.uk)

The input/output connections of a system.

A form of non-linear distortion that introduces frequencies not present in and musically unrelated to the original signal. These are invariably based on the sum and difference products of the original frequencies.

Something that happens occasionally and unpredictably, typically a fault condition.

A device that acts as an intermediary to two or more other pieces of equipment. For example, a MIDI interface enables a computer to communicate with MIDI instruments and keyboards.

The nominal signal level generated by an electric instrument like a guitar, bass guitar or keyboard. Typically around -25dBu. Instrument signals must be amplified to raise them to line-level.

A material that does not conduct electricity. (Also see conductor)

The input impedance of an electrical network is the ‘load’ into which a power source delivers energy. In modern audio systems the input impedance is normally about ten times higher than the source impedance - so a typical microphone preamp has an input impedance of between 1500 and 2500 Ohms, and a line input is usually between 10 and 50k Ohms.