gates so they do not trigger due to spurious noise such as when people move chairs. For vocal applications on stage, an optical microphone switch may be used. An infra-red sensor senses if somebody is in front of the microphone and switches on the microphone. Recording usages A good example of time-controlled noise gating is the well-known "gated reverb" effect heard on the drums on the Phil Collins hit single "In the Air Tonight", created by engineer-producer Hugh Padgham, in which the powerful reverberation added to the drums is cut off by the noise gate after a few milliseconds, rather than being allowed to decay naturally. This can also be achieved by: sending the "dry" snare signal to the reverb (or other process) unit, inserting a noise gate on the path of the reverb signal and connecting the snare sound to the side chain of the gate unit. With the gate unit set to "external sidechain" (or "external key"), the gate will respond to the snare signal level and "cut off" when that has decayed below the threshold, not the reverberated sound. It is a common production trick to use spurious combinations of side chain inputs to control longer, more sustained sounds. For example, a hi-hat signal can be used to control a sustained synthesized sound to produce a rhythmic melodic (or harmonic) signal which is perfectly in time with the hi-hat signal. A good example of this use of the device can be found on the Godley & Creme concept album Consequences. The album's story required the creation of a number of special sound effects that would convey the impression of natural disasters. For the "Fire" sequence, Godley and Creme used a noise gate, triggered by the sound of multitracked voices, that created the "voice" of a raging bushfire. During the recording of this segment, each time the voice signal began, it triggered the noise gate to open up another channel, which carried a pre-recorded loop of a crackling sound (created by overdubbing the sound of Bubble Wrap being popped in front of a microphone). The combined voices and crackling created an eerie and quite convincing "talking fire" effect. Multi-latch gating 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.