A physical obstruction to sound waves, such as a wall, or a large solid object. When sound waves reach a boundary they create a high pressure area at the surface which is typically perceived as a build up in the level of low frequencies.

The process of mixing two or more recorded tracks together and re-recording the result onto another track.

See Isolation Room

A single gain control to adjust the level of a range of frequencies passing through a filter or equaliser to be amplified or attenuated. The centre position is usually the 'flat' or 'no effect' position. This kind of control is found on shelf, parametric and graphic qualisers (high- and low-pass do not have cut/boost controls). 

A mechanical means of supporting a microphone above a sound source. Many microphone stands are supplied with a ‘boom arm’ affixed to the top of the stand’s main vertical mast. The term may also be applied to larger, remotely controlled microphone supports used in film and TV studios, or even to the handheld ‘fishpoles’ used by film and TV sound recordists.

A type of bayonet-locking, two-terminal connector used for professional video and digital audio connections. (See AES3-id)

A stereo microphone technique devised by Alan Blumlein in the early 1930s. It employs a pair of microphones with figure-eight polar patterns, mounted at 90 degrees to each other with the two diaphragms vertically aligned in so-called 'coincidence'. In this way, the signals from the two microphones differ only in their amplitudes (there can be no time-of-arrival or phase differences) in a way which accurately represents the angle of incidence of the sound sources.

A synthesizer than can generate two different sounds simultaneously (see multi-timbral).

The number of data bits replayed or transferred in a given period of time (normally one second). Normally expressed in terms of kb/s (kilo bits per second) or Mb/s (mega bits per second). For example, the bit rate of a standard CD is (2 channels x 16 bits per sample x 44.1 thousand samples per second) = 1411.2 kilobits/second. Popular MP3 file format bit rates range from 128kb/s to 320kb/s, while the Dolby Digital 5.1 surround soundtrack on a DVD-Video typically ranges between 384 and 448kb/s. (See Sample Rate)

A contraction of Binary digit, which may either be 1 or 0.