Patent ID: 8737636

Claim:
A method of producing an antinoise signal, said method comprising: producing the antinoise signal during a first time interval by applying a digital filter to a reference noise signal in a filtering domain having a first sampling rate; and producing the antinoise signal during a second time interval subsequent to the first time interval by applying the digital filter to the reference noise signal in the filtering domain, wherein during said first time interval, the digital filter has a first filter state, and wherein during the second time interval, the digital filter has a second filter state different than the first filter state, and wherein said method includes, in an adaptation domain having a second sampling rate that is lower than the first sampling rate, calculating the second filter state based on information from the reference noise signal and information from an error signal, and wherein said digital filter includes: a feedforward filter configured to filter a sum of the reference noise signal and a feedback signal to produce a filtered signal; and a feedback filter configured to filter the filtered signal to produce the feedback signal, wherein the antinoise signal is based on the filtered signal.