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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: 30/03/21

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A system designed to enable voice communication between rooms.

Tape Head

The part of a tape machine that transfers magnetic energy to the tape during recording, or reads it during playback.


The rate of the 'beat' of a piece of music measured in beats per minute.


Termination has two meanings in the context of audio. One application is simply the type of connector applied to a cable or wire, so a cable might be terminated in a 3-pin XLR plug, for example.

The second application refers to the electrical characteristics of some specific types of audio interface where the cable acts as a 'Transmission line'. This typically occurs where the cable is long relative to the wavelength of the signal it is carrying, so it most commonly applies to digital audio, video signals, and radio-frequency connections — although it can also apply to analogue audio cables when more than a few kilometres long.

When a cable operates as a transmission line it is said to have a 'characteristic impedance' — essentially the impedance presented at its input if the cable was infinitely long. To transfer a signal along the cable efficiently, it is vital that a end of a transmission line is terminated with the same impedance as its characteristic impedance. If it is left unterminated, the end of the cable behaces like a mirror, and signal energy is reflected back along the cable where upon it will interfere with the source signal. 

S/PDIF and Video cables normally require a 75 Ohm termination. RF cables usually require either 50 or 75 Ohms, depending on their construction. AES3 requires a 110 Ohm termination and RJ45-style Ethernet cables require 100 Ohms.

Test Tone

– A steady, fixed level tone recorded onto a multitrack recording, or passed over a signal connection to test the signal path and act as a reference when matching levels.


Total Harmonic Distortion. A measure of the linearity of a device. The THD+N measurement includes the noise contribution as well and is an indication of the quality of an audio product.


A MIDI connector which passes on the signal received at the MIDI in socket.


A bi-directional computer interface based on the PCI Express protocol, used for both data transfers and to connect display monitors (it supports DVI, HDMI, and VGA monitors via adapters). Introduced by Apple in 2011.


Referring to the tones that can be created by a synthesizer (see multi-timbral and bi-timbral)


The tonal 'colour' of a sound.

Tonader Power

Tonaderspeisung Power — more commonly called Tonader, T-power or A-B power — is a largely obsolete microphone powering system which was widely used on portable battery-powered audio equipment in the 1960s and '70s before the technically superior phantom powering system became more popular. T-Power operates with 9-12V DC with the positive rail connected to the hot side (pin 2) of a balanced audio connection, and the negative rail on the cold side (pin 3).

One of the potential weaknesses of T-Powering is that any power supply noise is inherently added directly to the wanted audio signal. T-Power is broadly similar in concept to the Plug-in or Bias Power arangement used on unbalanced consumer electret microphones, but with a higher supply voltage.

Tone Control

In hi-fi equipment 'tone controls' typically refers to bass and treble shelf equalisers, often using the Baxandall design. it may also refer to a low-pass filter in guitars and other electronic instruments. 


see S/PDIF.


The term dates back to multitrack tape where the tracks are physical stripes of recorded material, located side by side along the length of the tape.


The process of recording individual tracks to a multichannel recorder. Tracking is also often discussed in the context of MIDI guitar synthesizers or controllers where the MIDI output attempts to track the pitch of the guitar strings.


An electrical device in which two or more separate and electrically isolated coils of wire are wound around a common ferromagnetic core. Alternating Current passing through one coil creates a varying magnetic field which induces a corresponding current in the other coil(s). In audio applications transformers are often used to convey a signal without a direct electrical connection, thus providing 'galvanic isolation' between the source and destination. Winding a transformer with different numbers of turns for each coil allows the output voltage to be increased or decreased in direct proportion – a feature widely employed in mains power-supply transformers to reduce the mains voltage to something more appropriate for the circuitry, for example, or in microphone preamp step-up transformers.


A transient is a short-duration non-tonal, non-periodic sound element, usually of high amplitude and typically comprising high-frequency components. In the case of sounds generated by musical instruments, transients inherently present at the beginning of tonal waveforms are often critical to the instrument's aural signature and recognition. Transients can also be caused by a variety of fault conditions, such as incorrect clocking in digital systems.


When the length of an electrical cable is shorter than about 10% of the wavelength of the signal it conveys, the voltage and current are effectively the same at all points along the cable. However, if the cable is longer than 10% of the wavelength, the signal can be considered to propogate as electromagnetic waves along the cable, and this condition is referred to as a 'transmission-line'.

Triangle Wave

A symmetrical triangular shaped wave containing odd harmonics only, but with a lower harmonic content than the square wave.

TRS Plug

TRS refers to the 3-terminal 'Tip, Ring and Sleeve' format of various types of jack plug, typically used either for stereo unbalanced connections (such as on headphones) or mono balanced connections (such as for line-level signals). A 2-terminal alternative is also available, referred to as the TS (Tip, Sleeve) version, used for mono unbalanced signals. The term is applicable to A-type, mini-jack, B-type, and Bantam connectors.

True Peak Meter

– A form of digital audio meter which is capable of determining the absolute amplitude value of a digital signal by using oversampling to fully reconstruct the waveform.

Truss Rod

A metal bar within a guitar neck which is tensioned so as to counteract the tendency for the neck to bend under the tension of the strings.

TS Plug

TS refers to the 2-terminal 'Tip and Sleeve' format of various types of jack plug, typically used unbalanced mono audio connections or for CV and gate patching on monular synthesizers. A 3-terminal alternative is also available, referred to as the TRS (Tip, Ring, Sleeve) version. The term is applicable to A-type, and mini-jack connectors.

TT Jack Plug

See Bantam jack plug (TT is short for 'Tiny Telephone')


see Valve

Turnover frequency

Relates to filters and equalisers and is defined as frequency where the response has risen or fallen by 3dB. Sometimes  called the 'corner frequency' 


The colloquial term to describe a loudspeaker drive unit optimised for the reproduction of high frequencies. (See Woofer).