A Method for Detecting Undesirable Microphone Disturbance in ANC Applications

Active Noise Cancellation (ANC) technology is widely used in automobiles to reduce engine harmonic noise [3]. ANC systems require one or more microphones mounted in the cabin to monitor the harmonic noise level and provide feedback to the DSP algorithm. The ideal locations for the microphones are as close as possible to the passenger seating locations and away from any wind turbulence that can impact the diaphragm of the microphone. Excessive wind turbulence on the diaphragm can cause the ANC adaptive filter weights to be perturbed enough resulting in audible ‘pumping’ type artifacts.

For several practical reason it's not always possible to control the location of the microphones and hence a DSP software and/or mechanical solution needs to be incorporated in the system. This paper will primarily address the DSP software solutions to detect wind turbulence noise in ANC microphones so appropriate counter measures can be applied to eliminate the unwanted artifacts. The detector should be designed such that it is only sensitive to wind turbulence noise that can cause audible ANC artifacts and robust against any other disturbance that may incorrectly trigger the counter measure.

The paper will describe some of the challenges in detecting unwanted microphone turbulence noise in ANC microphones, and describe novel DSP algorithms to overcome some of these challenges.