MIC covering detection in personal audio devices

摘要

A personal audio device, such as a wireless telephone, includes noise canceling circuit that adaptively generates an anti-noise signal from a reference microphone signal and injects the anti-noise signal into the speaker or other transducer output to cause cancellation of ambient audio sounds. An error microphone may also be provided proximate the speaker to estimate an electro-acoustical path from the noise canceling circuit through the transducer. A processing circuit uses the reference and/or error microphone, optionally along with a microphone provided for capturing near-end speech, to determine whether one of the reference or error microphones is obstructed by comparing their received signal content and takes action to avoid generation of erroneous anti-noise.

主权项

1. A personal audio device, comprising:
a personal audio device housing; a transducer mounted on the housing for reproducing an audio signal including both source audio for playback to a listener and an anti-noise signal for countering the effects of ambient audio sounds in the proximity of an acoustic output of the transducer; a plurality of microphones, including a first microphone mounted on the housing that, when unobstructed, provides a first microphone signal indicative of the ambient audio sounds, wherein a second microphone of the plurality of microphones is mounted on the housing and that, when unobstructed, provides a second microphone signal indicative of the ambient audio sounds; and a processing circuit that implements a first adaptive filter having a response that generates the anti-noise signal from the first microphone signal, a second adaptive filter for generating shaped source audio from the source audio and a combiner for removing the shaped source audio from the second microphone signal to generate an error signal provided to a coefficient control block that controls coefficients of the first adaptive filter, wherein the processing circuit implements a first signal level detector for detecting a first amplitude of the first microphone signal to generate a first microphone level signal and at second signal level detector for detecting a second amplitude of the second microphone signal to generate a second microphone level signal, and wherein the processing circuit further compares the first microphone level signal and a signal level of one of the plurality of microphones other than the first microphone and, in response to determining that a first differences between the first microphone level signal and the signal level of the one of the plurality of microphones other than the first microphone indicates that the first microphone is at least partially obstructed, halts adaptation of the first adaptive filter so that first coefficients of the first adaptive filter are maintained at their existing values to prevent the anti-noise signal from being generated erroneously, and wherein the processing circuit compares the second microphone level signal and a signal level of one of the plurality of microphones other than the second microphone, and in response to determining that a second difference between the second microphone level signal and the signal level of the one of the plurality of microphones other than the second microphone indicates that the second microphone is at least partially obstructed, halts adaptation of the first adaptive filter and the second adaptive filter and resets the first coefficients and the second coefficients to predetermined values.