Feedback cancellation with low frequency input
First Claim
1. A method for canceling feedback in an acoustic system comprising a microphone, a speaker, a signal path between the microphone and the speaker, means for detecting presence of feedback between the speaker and the microphone, and first adaptive feedback cancellation filter means for compensating at least partly a possible feedback signal, the method comprising:
- using a LMS algorithm for generating filter coefficients for the first adaptive feedback cancellation filter means and for generating identical filter coefficients for a second adaptive feedback cancellation filter means;
using at least one highpass filter to prevent low-frequency signals from the signal path from entering the LMS algorithm; and
using the second adaptive feedback cancellation filter means and a noise generator for providing low-frequency input for the LMS algorithm.
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Abstract
The invention relates to a method for canceling feedback in an acoustic system comprising a microphone, a signal path, a speaker and means for detecting presence of feedback between the speaker and the microphone, the method comprising providing a LMS algorithm for processing the signal; where the LMS algorithm operates with a predetermined adaptation speed when feedback is not present; where the LMS algorithm operates an adaptation speed faster than the predetermined adaptation speed when feedback is present, and where the means for detecting the presence of feedback is used to control the adaptation speed selection of the LMS algorithm. The invention further relates to a method comprising using a highpass filter to prevent low-frequency signals from entering the LMS algorithm. The invention still further relates to a method comprising using bandwidth detection means for determining the presence of a feedback signal. The invention also relates to hearing aids for implementing these methods.
20 Citations
10 Claims
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1. A method for canceling feedback in an acoustic system comprising a microphone, a speaker, a signal path between the microphone and the speaker, means for detecting presence of feedback between the speaker and the microphone, and first adaptive feedback cancellation filter means for compensating at least partly a possible feedback signal, the method comprising:
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using a LMS algorithm for generating filter coefficients for the first adaptive feedback cancellation filter means and for generating identical filter coefficients for a second adaptive feedback cancellation filter means; using at least one highpass filter to prevent low-frequency signals from the signal path from entering the LMS algorithm; and using the second adaptive feedback cancellation filter means and a noise generator for providing low-frequency input for the LMS algorithm. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A hearing aid comprising:
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a microphone; a speaker; a signal path between the microphone and the speaker, and which includes an amplifier; means for detecting feedback between the speaker and the microphone; first adaptive feedback cancellation filter means for at least partly compensating a possible feedback signal; memory means including a LMS algorithm for generating filter coefficients for the first adaptive feedback cancellation filter means and for generating identical filter coefficients for a second adaptive feedback cancellation filter means; at least one highpass filter for preventing low-frequency signals from the signal path from entering the LMS algorithm;
wherebythe second adaptive feedback cancellation filter means and a noise generator provides low-frequency input for the LMS algorithm. - View Dependent Claims (10)
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Specification