See Head Related Transfer Functions

A stereo audio vectorscope which displays the stereo sound image as a Lissajous Figure to assess the correlation and stereo width between channels, as revealed by the phase and amplitude relationships between the two channels.

The two audio channels are plotted on diagonal axes such that a left-only signal is shown as a diagonal line from top-left to bottom-right, while a right-only signal runs from top-right to bottom-left. An identical signal on both channels (dual-mono) results in a thin vertical line, while identical signals in opposite polarity create a thin horizontal line. Normal stereo creates the appearance of a circular tangled ‘ball of string’.

A near-coincident stereo microphone array described in detail by British audio engineer Michael Gerzon (1945 – 1996) but also credited to Tony Faulkner. It comprises a pair of cardioid microphones with capsules spaced 5cm apart at a mutual angle of 120°. The resulting SRA is 130 degrees. This technique captures both time and level differences between channels, and is comparable to similar techniques such as ORTF, RAI, DIN, NOS and others, but with a noticeably smaller spacing and wider mutual angle. It is often used with a shuffling process to enhance the sense of spaciousness at low frequencies.

A set of pioneering technologies developed by the Walt Disney Studios in the late 1930s for the film Fantasia. It was the first commercial surround sound system, which pioneered the use of pan-pots for sound positioning, multitrack recording, overdubbing, click tracks for synchronisation, control tracks for automatic gain control, and more.

An eponymously named near-spaced stereo microphone system developed by Eberhard SengPiel. It comprises a pair of cardioid microphones with capsules spaced 25cm apart at a mutual angle of 90°. The resulting SRA is 90 degrees. This technique captures both time and level differences between channels, and is comparable to similar techniques such as ORTF, RAI, DIN, NOS and others.

Identical audio content carried in both the left and right channels of a stereo system (ie. panned centre), resulting in a phantom centre sound image.

Dr Harvey Fletcher (1884 – 1981) was an American physicist working for Bell Laboratories on the development of  Stereophonic Sound, amongst other things, in the early 1930s. He was a contemporary of Alan Blumlein but was developing stereo techniques entirely independently.

See Double Mid-Sides Array

An extension of the Mid-Sides microphone concept in which a second Mid microphone is added to the array, but facing directly backwards. This system requires only three audio channels, but can be decoded to create five channels as the shared Sides mic is used with the rearward Mid mic to generate rear left and rear right signals suitable for surround sound applications. Sometimes referred to as the DMS format and employed where a compact surround-sound mic array is required.

An acronym for a German standards organisation founded in 1917: Deutsches Institut für Normung. Amongst many audio standards created by this organisation, the DIN stereo microphone array comprises a pair of near-spaced cardioid microphones with capsules spaced 20cm apart at a mutual angle of 90°. The resulting SRA is 101 degrees. This technique captures both time and level differences between channels, and is comparable to similar techniques such as ORTF, RAI, EBS, NOS, and others.