Patent ID: 8515089
Filing Date: 2013-08-20
Classification: G10K

Abstract:
1. A portable audio device comprising: an earpiece speaker having an input to receive an audio signal; active noise cancellation (ANC) circuitry to provide an anti-noise signal at the input of the earpiece speaker to control ambient acoustic noise outside of the device that is heard by a user of the device; a first microphone to pick up the ambient acoustic noise, wherein the ANC circuitry includes an adaptive filter that generates the anti-noise signal using a representation of the ambient acoustic noise as picked up by the first microphone; noise measurement circuitry having a first input coupled to an output of a second microphone, a second input coupled to receive the audio signal and the anti-noise signal, a first filter that models the earpiece speaker and the second microphone, a differencing unit having a first input coupled to the output of the second microphone and a second input coupled to an output of the first filter, and a second filter that models the earpiece speaker and the second microphone, wherein the audio signal is to pass through the first and second filters and the anti-noise signal is to pass through the first filter and further wherein the second microphone is positioned closer to the earpiece speaker than the first microphone and is to pick up (a) sound emitted from the earpiece speaker and (b) the ambient acoustic noise; and control circuitry coupled to receive an estimate of the ambient acoustic noise from the noise measurement circuitry and to deactivate the ANC circuitry in response to determining that an estimate of how much sound emitted from the earpiece speaker has been corrupted by said ambient acoustic noise, indicates insufficient corruption by noise.