US 6,434,247 B1Granted

Feedback cancellation apparatus and methods utilizing adaptive reference filter mechanisms

AssigneeGN ReSound A/S

InventorsJames Mitchell Kates, John Laurence Melanson

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Abstract

A feedback cancellation system for a hearing aid or the like adapts a first filter in the feedback path that models the quickly varying portion of the hearing aid feedback path, and adapts a second filter in the feedback path that is used either as a reference filter for constrained adaptation or to model more slowly varying portions of the feedback path. The second filter is updated only when the hearing aid signals indicate that an accurate estimate of the feedback path can be obtained. Changes in the second filter are then monitored to detect changes in the hearing aid feedback path. The first filter is adaptively updated at least when the condition of the signal indicates that an accurate estimate of physical feedback cannot be made. It may be updated on a continuous or frequent basis.

Claims20

Dependent claims

An audio system comprising:

means for providing an audio signal;
feedback cancellation means including means for estimating a physical feedback signal of the audio system, and means for modelling a signal processing feedback signal to compensate for the estimated physical feedback signal;
subtracting means, connected to the means for providing an audio signal and the output of the feedback cancellation means, for subtracting the signal processing feedback signal from the audio signal to form a compensated audio signal;
audio system processing means, connected to the output of the subtracting means, for processing the compensated audio signal;
means for estimating the condition of the audio signal and generating a control signal based upon the condition estimate;
wherein said feedback cancellation means forms a feedback path from the output of the audio system processing means to the input of the subtracting means and includes:
a reference filter, and
a current filter,
wherein the reference filter varies only when the control signal indicates that the audio signal is suitable for estimating physical feedback, and wherein the current filter varies at least when the control signal indicates that the signal is not suitable for estimating physical feedback.

6 more elements

Dependencies are inferred from the claim text.