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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: 01/02/24

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B-Type Plug

A professional form of quarter-inch jack plug derived from the telecommunications industry where it is known as the PO316. It has three terminals (tip-ring-sleeve) and is widely used for balanced connections on professional patch bays. Although of similar overall length and diameter to the domestic A-type plug, it has a much smaller tip and is incompatible. A miniature version is available for high-density patchbays, called the TT or Bantam jack-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 within an all-embracing overall electrostatic 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 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 (called a common mode signal) because the impedance to ground is identical for each wire. As there is therefore no voltage difference between the two signal wires, any interference is therefore ignored (rejected) completely by the receiver.

Band-pass Filter (BPF)

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

Band-stop Filter

A filter that removes or attenuates frequencies in a defined range or bandwidth, while letting through those frequencies both above and below the band. A wider form of notch filter.


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 miniaturised form of the PO316 professional jack plug derived from the telecommunications industry and widely used for balanced connections on professional high-density patch bays. (cf. B-Type Plug)

Bass Reflex

A bass reflex loudspeaker employs a cabinet with a vent (or port) which allows some of the energy from the rear of the driver unit's diaphgram to supplement that from the front at low frequencies, improving the overall efficiency and allow a greater bass extension (but with a steeper roll-off) for a given size of cabinet.

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 Trap

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


A type of simple audio shelf equaliser or bass/treble tone control invented by English electronics engineer Peter Baxandall (1921-1995). 

Beta Version

Software which is not fully tested and may include bugs.


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


An ultrasonic signal used in analogue recording to improve the linearity of the magnetic recording process and thus ensure the accuracy of the recorded audio signal. The bias freqeuency is typically between 80kHz and 150kHz. It is also used 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.


Strictly, a term referring to using two ears to listen to sounds, usually with a view to identifying source direction.

However, more general usage has come to use the term to refer to a specific form of two-channel audio intended exclusively for auditioning via headphones or ear buds. Binaural recording techniques involve the use of two spaced microphones, usually with a baffle or object placed between them. The idea is to capture the typical inter-aural time delays and high-frequency sound shadowing effects of the human head which play critical roles in enable the accurate determination of directivity cues.


Basic Input-Output System — Part of a computer operating system stored on a on ROM permanent memory chip rather than on hard-disk. The BIOS controls basic routines such as accessing the disk drives and managing data flow around the computer.


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

Bit 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. (See Sample Rate)


Alan Dower Blumlein (1903-1942) was an electronics engineer who was instrumental in the development of stereo recording techniques and equipment in the 1930s when working for EMI. 

Blumlein Array

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 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 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). 


The process of mixing two or more recorded tracks together and re-recording the result 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 which is typically perceived as a build up in the level of low frequencies.

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, allowing woodwind players to control synthesizers.


Buffer — An electronic circuit designed to isolate the output of a source device from loading effects due to the input impedance of destination devices.