Ear-wearable device with active noise cancellation system that uses internal and external microphones

Abstract

An ear-wearable device is operable to receive a reference signal from outside an ear canal of a user and an error signal from inside of the ear canal. A physical propagation path between the outside and inside of the ear canal defines a primary path, and amplified sound produced inside of the ear canal propagates over a secondary path to combine with direct noise at the ear canal. A noise signal inside the ear canal is estimated from the reference signal based on estimate of the primary and secondary paths. The estimated noise signal and the error signal are used to produce coefficients of an adaptive filter. The adaptive filter is used to produce an anti-noise signal, which is used actively cancel noise in the ear canal.