Editing Envelope detector (section)

== Audio ==
{{See also|Noise gate#Trance gating}}
An envelope detector is sometimes referred to as an '''envelope follower''' in [[music]]al environments. It is still used to detect the [[amplitude]] variations of an incoming signal to produce a control signal that resembles those variations. However, in this case the input signal is made up of audible frequencies.

Envelope detectors are often a component of other circuits, such as a [[Audio level compression|compressor]] or an [[auto-wah]] or envelope-followed filter. In these circuits, the envelope follower is part of what is known as the "[[side chain (sound)|side chain]]", a circuit which describes some characteristic of the input, in this case its volume.

Both [[dynamic range compression|expanders]] and [[audio level compression|compressors]] use the envelope's output voltage to control the gain of an amplifier. Auto-wah uses the voltage to control the [[cutoff frequency]] of a filter. The [[voltage-controlled filter]] of an [[analog synthesizer]] is a similar circuit.

Modern envelope followers can be implemented: 
# directly as [[electronic hardware]],
# or as software using either a [[digital signal processor]] (DSP) or
# on a general-purpose CPU.