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Abstract

A new subband feedback cancellation scheme is proposed, capable of providing additional stable gain without introducing audible artifacts. The subband feedback cancellation scheme employs a cascade of two narrow-band filters A.sub.i (Z) and B.sub.i (Z) along with a fixed delay, instead of a single filter W.sub.i (Z) and a delay to represent the feedback path in each subband. The first filter, A.sub.i (Z), is called the training filter, and models the static portion of the feedback path in i.sup.th subband, including microphone, receiver, ear canal resonance, and other relatively static parameters. The training filter can be implemented as a FIR filter or as an IIR filter. The second filter, B.sub.I (Z), is called a tracking filter and is typically implemented as a FIR filter with fewer taps than the training filter. This second filter tracks the variations of the feedback path in the i.sup.th subband caused by jaw movement or objects close to the ears of the user.

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First Claim