Patent ID: 9082389
Filing Date: 2015-07-14
Classification: G10K

Abstract:
1. A portable personal listening audio device comprising: an earpiece speaker having an input to receive an audio signal; a reference microphone to pick up background acoustic noise outside of the device; an error microphone to pick up sound emitted from the earpiece speaker; and active noise cancellation (ANC) circuitry having a pre-shaping digital filter whose input is coupled to the reference microphone and whose output is in series with, and in front of, an adaptive digital filter, the adaptive digital filter is to be adjusted by an adaptive filter controller based on input from a) the audio signal, b) the reference microphone and c) the error microphone, to provide an anti-noise signal to an input of the earpiece speaker to control the background acoustic noise that is heard by a user of the device, and wherein the pre-shaping digital filter is configured to be minimum phase and to present between at least 2 dB but no more than 15 dB more gain over a low audio frequency band than over a high audio frequency band.