Multiple Microphone Miracles - Rejecting Unwanted Data from Your Measurements

Single microphones may not be able to distinguish a sound source of interest from others in the vicinity, hear a source in windy environments, or measure faint signals which may be below the microphone noise floor.  However, adding just a single additional microphone can help resolve all these issues.  This paper reviews how ICP microphones work and explains their noise floors.  Next, we'll explain how to combine the signals from two or more microphones to tell one source from another, filter unwanted sources (like flow-induced pressures) from data, and reduce noise floors to measure very low signals.  We process the signal pairs using cross-spectral analysis to calculate the coherence between the signals.  The coherence can help extract a desired signal or reject undesired ones.