Unwanted sound picked up by microphones on one instrument from other nearby instruments.

An accurate loudspeaker intended for critical sound auditioning purposes.

Sony/Philips Digital InterFace. Pronounced either ‘S-peedif’ or ‘Spudif’. A stereo or dual-channel self-clocking digital interfacing standard employed by Sony and Philips in consumer digital hi-fi products. The S/PDIF signal is essentially identical in data format to the professional AES3 interface, and is available as either an unbalanced electrical interface (using phono connectors and 75ohm coaxial cable), or as an optical interface called TOSlink.

A means of arranging two or more microphone capsules such that they receive sound waves from different directions at different times - these timing differences being used to convey information about the relatice directions of those sound sources. The technique is usually used with omnidirectional microphones, although directional mics can also be employed. The best known form of spaced array is the Decca Tree. Mono-compatibility is often reduced because the timing differences between channels often results in comb-filtering colouration when the channels are summed to mono.

The use of materials and construction techniques with the aim of preventing unwanted sound from entering or leaving a room.

An early recording technique pioneered by Les Paul and others which was a simple form of overdubbing to build up a mix of sources. Also, the world's best recording technology magazine (see www.soundonsound.com).

A dedicated interface to transfer audio signals in and out of a computer. A Sound Card can be installed internally, or connected externally via USB2 or FireWire, and they are available in a wide range of formats, accommodating multiple analogue or digital audio signals (or both) in and out, as well as MIDI data in and out.

A term used to describe a cable used to carry multiple individual audio signals, typically between a stage and mixing console in live sound applications.

Sample Multiplexing (see ADAT ).

The Society of Motion Picture and Television Engineers (www.smpte.org) an American standards body. The term is also used to refer to a form of time code developed for the film industry but now extensively used in music and recording. SMPTE is a real-time digital code describing hours, minutes, seconds and film or video frames. Usually conveyed as an audible warble.