SOUND ON SOUND
Relating to the waveform characteristics of an AC signal such as an audio waveform. It decribes the ratio between the peak amplitude and the RMS level. The 'peakier' or more dynamic the signal, the greater the crest factor. Crest Factor is normally expressed in decibels.
A pure sine wave has a crest factor of 1.414 or 3.01dB, while a triangle wave is 4.77dB and a square wave 0dB.
A 'Dummy Head' is a binaural recording array which intentionally resembles (to a greater or lesser degree) the size and shape (and sometimes also the density) of the average human head, with two microphones placed on opposite sides in the positions of the ear canals. The idea is to capture passing sound waves in the sa,e way as a normal listener would perceive them, with the correct inter-aural time delays and head shadowing effects which are critical to assessing directional cues.
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.
A microphone — typically with a hypercardioid capsule — which has a perforated tube fitted in front of the diaphragm to try and create a substantially narrowed polar pattern.
Sound waves directly on-axis pass straight down the tube to reach the diaphragm without being affected in any significant way. However, this tube also has a number of slots or holes along its length which allow off-axis sound waves to enter at different points. The resulting different path lengths to the diaphragm create phase shifts resulting in partial cancellation and thus reduced sensitivity to sounds from the side of the tube. Hence the design's name of an 'interference tube microphone'. Alternative names include 'rifle' or 'shotgun' mic, principally because in the film and TV industries the mic is often fitted to a handle, resembling a firearm.
The cancellation of off-axis sounds is rarely perfect or consistent, resulting in varying amounts of attenuation for sound sources of different frequencies and at different angles of incidence. This means that off-axis sounds, while genreally attenuated, are also substantialluy coloured , and if the angle between mic and sound source is varied the cancellation dips move up and down the spectrum to give a phaser-like colouration or whoosing effect.
A method of controlling dynamic range in which the source signal is split, with one path being heavily compressed before being recombined with the original signal. The result is a form of 'upwards compression' in which low level signals are raised in level while high level elements are left unchanged. This technique preserves transients and is therefore particularlty popular for processing drum tracks. (Conventional downwards compression inherently modifies transients.)
Often known as New York Compression, and as London Compression!
There is a full explanation of the technique here: https://www.soundonsound.com/techniques/parallel-compression
