Noise gate
A common application is with electric guitar to remove hum and hiss noise caused by distortion effects units.
The release control is used to define the length of time the gate takes to change from open to fully closed.
The attack control is used to define the length of time the gate takes to change from closed to fully open.
The hold control is used to define the length of time the gate will stay fully open after the signal falls below the threshold, and before the release period is commenced.
The hold control is often set to ensure the gate does not close during short pauses between words or sentences in a speech signal.
Rock musicians may also use small portable "stompbox" units to control unwanted noise from their guitar amplification systems.
In audio post-processing, noise gating reduces steady noise sources such as rumble from LP records, hiss from audio tape, static from a radio or amplifier, and hum from a power system, without greatly affecting the source sound.
Common digital audio editing software packages such as CoolEdit and Audacity include easy-to-use digital noise gating code: the user selects a segment of audio that contains only static, and the amplitude levels in each frequency band are used to determine the threshold levels to be applied across the signal as a whole.
Noise gating works well when the static is steady and either narrowly confined in frequency (e.g. hum from AC power) or well below the main signal level (15 dB minimum is desirable).
In cases where the signal merges with the background static (for example, the brushed drum sounds in the "Sun King" track on the Beatles album Abbey Road) or is weak compared to the noise (as in very faint tape recordings, the noise gating can add artifacts that are more distracting than the original static.
It is a common production trick to use spurious combinations of side chain inputs to control longer, more sustained sounds.
The album's story required the creation of a number of special sound effects that would convey the impression of natural disasters.
[citation needed] "One thing I did that I think gave the album a certain sound was I Kepexed everything," said Alan Parsons, engineer on Pink Floyd's The Dark Side of the Moon.
"[5] The invention of a technique, called multi-latch gating by Jay Hodgson, common in classical music recordings for years, is often credited to producer Tony Visconti, whose use on David Bowie's "Heroes" may have been the first in rock.
"Bowie's performance thus grows in intensity precisely as ever more ambience infuses his delivery until, by the final verse, he has to shout just to be heard....The more Bowie shouts to be heard, in fact, the further back in the mix Visconti's multi-latch system pushes his vocal tracks [dry audio being perceived as front and ambience pushing audio back in the mix], creating a stark metaphor for the situation of Bowie's doomed lovers shouting their love for one another over the Berlin wall.
Examples include DJ Nexus's "Journey into Trance" (1:11), Chic's "Everybody Dance", and Diana Ross's "Upside Down".
