''The acoustic sensor 140 may generate acoustic measurement data continuously, or at a sampling rate that may be fixed or variable. In one embodiment, multiple acoustic sensors are used to filter noise from relevant acoustic signals and preprocessing of the acoustic signal using signal processing techniques can be used to simplify classification calculations. Examples of the acoustic sensor 140 include a microphone or like mechanism which detects acoustics and sounds. The acoustic sensor 140 provides the detected acoustics and sound to an acoustic processor 145''

https://www.google.com/patents/US8311522

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