Patent ID: 9368099
Filing Date: 2016-06-14
CPC Classification: G10K

Claim Text:
1. A personal audio device, comprising: a personal audio device housing; a transducer mounted on the personal audio device housing for reproducing an audio signal including both source audio for playback to a listener and an anti-noise signal for countering effects of ambient audio sounds in an acoustic output of the transducer; a reference microphone mounted on the personal audio device housing for providing a reference microphone signal indicative of the ambient audio sounds; an error microphone mounted on the personal audio device 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; and a processing circuit that implements an adaptive filter having a response that generates the anti-noise signal from the reference microphone signal to reduce a presence of the ambient audio sounds heard by the listener, wherein the processing circuit implements a first fixed filter having a predetermined response acting in functional series with the adaptive filter, wherein the first fixed filter alters an anti-noise signal component of the audio signal, wherein the processing circuit further implements a secondary path adaptive filter having a secondary path response that shapes the source audio to generate shaped source audio and a combiner that removes the shaped source audio from the error microphone signal to provide an error signal indicative of the combined anti-noise and ambient audio sounds delivered to the listener, wherein the processing circuit further subtracts the output of the first fixed filter from the source audio provided to the secondary path adaptive filter and adds a signal generated from the output of the adaptive filter to the source audio provided to the secondary path adaptive filter to prevent a frequency response of the first fixed filter from appearing in the error signal, wherein the processing circuit shapes the response of the adaptive filter in conformity with the error microphone signal and the reference microphone signal by adapting the response of the adaptive filter to minimize the ambient audio sounds at the error microphone.