Patent ID: 9214150
Filing Date: 2015-12-15
Classification: G10K

Abstract:
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 an acoustic output of the transducer; a first combiner for combining a source audio signal containing the source audio and the anti-noise signal to provide an output signal for reproduction by the transducer; a reference microphone mounted on the housing for providing a reference microphone signal indicative of the ambient audio sounds; an error microphone mounted on the housing in proximity to the transducer for providing an error microphone signal indicative of the acoustic output of the transducer and the ambient audio sounds at the transducer; a controllable noise source for providing a noise signal; a source audio detector having an input coupled to the source audio signal for determining whether source audio of sufficient amplitude is present in the source audio signal; and a processing circuit that generates the anti-noise signal from the reference microphone signal to reduce the presence of the ambient audio sounds heard by the listener in conformity with an error signal and the reference microphone signal, wherein the processing circuit implements a secondary path adaptive filter having a secondary path response that shapes the source audio to generate shaped source audio and a second combiner that removes the shaped source audio from the error microphone signal to provide the error signal, and wherein the processing circuit, in response to the source audio detector determining that source audio of sufficient amplitude is not present in the source audio signal, selectively injects noise from the controllable noise source into the secondary path adaptive filter and further injects the noise into the first combiner in place of or in combination with the source audio signal to cause the secondary path adaptive filter to continue to adapt when the source audio is absent or has reduced amplitude, and wherein the processing circuit further controls the controllable noise source in conformity with an output of the secondary path adaptive filter.