|Microsoft DirectX 9.0|
The Gargle Filter is an audio effect transform filter.
The Gargle filter modulates the waveform passing through it by multiplying the waveform by another waveform that is mathematically generated within the filter. The modulating waveform is, by default, a triangular wave. The property sheet also offers the alternative of a square wave. You can set the frequency of the modulating wave through the filter's property sheet. At low modulation frequencies, the effect sounds like a tremolo. At higher modulation frequencies, it sounds like a distortion, adding extra frequencies above and below the original unmodulated sound.
Source: (SDK root)\Samples\C++\DirectShow\Filters\Gargle