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Welcome to Sound On Sound's indispensible, regularly updated, explanations of technical terms from the fields of Recording, Audio Production, Music Technology, MIDI, Music Software, Audio Plug-ins, Mac and PC Computing, Live Sound, Acoustics, Electronics and more...

If we do not explain a particular term below, please email and we will add it to our next update.

Last updated: 04/08/20

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B-Type Plug

A professional form of jack plug derived from the telecommunications industry and also known as the PO316. Widely used for balanced mic and line-level connections on professional patch bays. (cf. A-Type Plug)

Back Electret

A form of electrostatic or capacitor microphone.


A safety copy of software or other digital data. A popular saying is that unless data exists in three physically separate locations at the same time, it hasn’t been backed up properly!


This word has several meanings in recording. It may refer to the relative levels of the left and right channels of a stereo recording (eg. Balance Control), or it may be used to describe the relative levels of the various instruments and voices within a mix (ie. Mix balance).

Balanced Wiring

Where protection from electromagnetic interference and freedom from earth references are required, a balanced interface is used. The term ‘balanced’ refers to identical (balanced) impedances to ground from each of two signal carrying conductors which are enclosed, again, within an all-embracing overall screen. This screen is grounded (to catch and remove unwanted RFI), but plays no part in passing the audio signal or providing its voltage reference. Instead, the two signal wires provide the reference voltage for each other - the signal is conveyed ‘differentially’ and the receiver detects the voltage difference between the two signal wires. Any interference instils the same voltage on each wire (common mode) because the impedance to ground is identical for each, and as there is therefore no voltage difference between the signal wires, the interference is ignored completely by the receiver.
Signals conveyed over the balanced interface may appear as equal half-level voltages with opposite polarities on each signal wire - the most commonly described technique. However, modern systems are increasingly using a single-sided approach where one wire carries the entire signal voltage and the other a ground reference for it. Some advantages of this technique include less complicated balanced driver stages, and connection to an unbalanced destination still provides the correct signal level, yet the interference rejection properties are unaffected. Effective interference rejection requires both the sending and receiving devices to have balanced output and input stages respectively.

Band-pass Filter (BPF)

A filter that removes or attenuates frequencies above and below the centre frequency at which it is set, and only passes a specific range of frequencies. Band-pass filters are often used in synthesizers as tone shaping elements.


The range of frequencies passed by an electronic circuit such as an amplifier, mixer or filter. The frequency range is usually measured at the points where the level drops by 3dB relative to the maximum. (See also Q)


A specific configuration of sounds or other parameters stored in memory and accessed manually or via MIDI commands.

Bantam Plug

Also known as TT or Tiny Telephone Plugs. A professional form of miniature jack plug derived from the telecommunications industry and widely used for balanced mic and line-level connections on professional patch bays. (cf. B-Type Plug)

Bass Response

The frequency response of a loudspeaker system at the lower end of the spectrum. The physical size and design of a loudspeaker cabinet and the bass driver (woofer) determine the low frequency extension (the lowest frequency the speaker can reproduce at normal level) and the how quickly the signal level falls below that frequency.

Bass Tip-up

see Proximity Effect.

Bass Trap

A special type of acoustic absorber which is optimised to absorb low frequency sound waves.

Beta Version

Software which is not fully tested and may include bugs.


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


A high-frequency signal used in analogue recording to improve the accuracy of the recorded signal and to drive the erase head. Bias is generated by a bias oscillator.


A counting system based on only two states: 1s and 0s. It is ideal for electronic equipment where it can be represented as high and low voltages, light on/off, N-S or S-N magnetic domains, etc.


Part of a computer operating system (basic input-output system) held on ROM rather than on disk. This handles basic routines such as accessing the disk drive.


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

Bit Rate (see also Sample Rate)

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.

Blumlein Array

A stereo coincident microphone technique devices by Alan Blumlein in the early 1930s, employing a pair of microphones with figure-eight polar patterns, mounted at 90 degrees to each other with the two diaphragms vertically aligned.


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


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.

Boost/Cut Control

A single gain control which allows the range of frequencies passing through a filter to be either amplified or attenuated. The centre position is usually the 'flat' or 'no effect' position.


See Isolation Room


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


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.

Boundary Layer Microphone

A specialised microphone where the diaphragm is placed very close to a boundary (eg. wall, floor or ceiling). In this position the direct and reflected sound adds constructively, giving a 6dB increase in sensitivity. It also avoids the comb-filtering that can occur when a conventionally placed microphone captures the direct sound along with strong first reflections from nearby boundaries. Also known as PZM or Pressure Zone Microphone.


Beats Per Minute.

Breath Controller

A device that converts breath pressure into MIDI controller data.
Buffer - An electronic circuit designed to isolate the output of a source device from loading effects due to the input impedance of destination devices.

Buffer Memory

A buffer is essentially a short term data storage facility used to accommodate variable data read or write periods, temporarily storing data in sequence until it can be processed or transferred by or to some other part of the system.


Slang term for a software fault or equipment design problem.


(Also sometimes referred to as a buss) An electrical signal path along which multiple signals may travel. A typical audio mixer contains several (mix) buses which carry the stereo mix, subgroups, the PFL signal, the aux sends, and so on. Power supplies are also fed along buses.


A collection of digital data comprising eight bits.