Claims
- 1. A hearing aid comprising:
a microphone for converting sound into an audio signal; feedback cancellation means including means for estimating a physical feedback signal of the hearing aid, and means for modeling a signal processing feedback signal to compensate for the estimated physical feedback signal; subtracting means, connected to the output of the microphone 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; hearing aid processing means, connected to the output of the subtracting means, for processing the compensated audio signal; and speaker means, connected to the output of the hearing aid processing means, for converting the processed compensated audio signal into a sound signal; wherein said feedback cancellation means forms a feedback path from the output of the hearing aid processing means to the input of the subtracting means and comprises
a first filter for modeling at least one near constant factor in a physical feedback path, and a second, adaptive, filter for modeling variable factors in the physical feedback path.
- 2. The hearing aid of claim 1, wherein the first filter is a fixed filter.
- 3. The hearing aid of claim 1, wherein the first filter is an adaptive filter having an adaptation rate substantially slower than an adaptation rate of the second filter.
- 4. The hearing aid of claim 1, wherein the near constant factor is selected from the group consisting of a frequency response of the microphone, a frequency response of the speaker means, a frequency response of the processing means, and a frequency response of a vent.
- 5. The hearing aid of claim 1, wherein the first filter models at least two near constant factors.
- 6. The hearing aid of claim 5, wherein the near constant factors are selected from the group consisting of a frequency response of the microphone, a frequency response of the speaker means, a frequency response of the processing means, and a frequency response of a vent.
- 7. A hearing aid comprising:
a first microphone for converting sound into a first audio signal; a second microphone for converting sound into a second audio signal; feedback cancellation means including means for estimating physical feedback signals to each microphone of the hearing aid, and means for modeling a first signal processing feedback signal to compensate for the estimated physical feedback signal to the first microphone and a second signal processing feedback signal to compensate for the estimated physical feedback signal to the second microphone; means for subtracting the first signal processing feedback signal from the first audio signal to form a first compensated audio signal; means for subtracting the second signal processing feedback signal from the second audio signal to form a second compensated audio signal; beamforming means, connected to each subtracting means, to combine the compensated audio signals into a beamformed signal; hearing aid processing means, connected to the beamforming means, for processing the beamformed signal; and speaker means, connected to the output of the hearing aid processing means, for converting the processed beamformed signal into a sound signal; wherein said feedback cancellation means includes
a first filter, connected to the output of the hearing aid processing means, for modeling at least one near constant factor in one of the physical feedback paths; a second, adaptive, filter, connected to the output of the first filter and providing an input to the first subtraction means, for modeling variable factors in the first feedback path; and a third, adaptive, filter, connected to the output of the first filter and providing an input to the second subtraction means, for modeling variable factors in the second feedback path.
- 8. The hearing aid of claim 7, wherein the first filter is a fixed filter.
- 9. The hearing aid of claim 7, wherein the first filter is an adaptive filter having an adaptation rate substantially slower than an adaptation rate of the second or third filters.
- 10. The hearing aid of claim 7, wherein the near constant factor is selected from the group consisting of a frequency response of the first microphone, a frequency response of the second microphone, a frequency response of the speaker means, a frequency response of a first vent; and a frequency response of a second vent.
- 11. The hearing aid of claim 7, wherein the first filter models at least two near constant factors.
- 12. The hearing aid of claim 11, wherein the near constant factors are selected from the group consisting of a frequency response of the first microphone, a frequency response of the second microphone, a frequency response of the speaker means, a frequency response of a first vent; and a frequency response of a second vent.
- 13. A method of compensating feedback signals in a hearing aid comprising the steps of:
turning on the hearing aid; configuring the hearing aid to operate in an open loop manner; inserting a test signal into a hearing aid output; estimating a physical feedback path of the hearing aid based on the test signal; designing a first filter modeling at least one near constant factor in the estimated physical feedback path; designing a second, adaptive, filter modeling variable factors in the estimated physical feedback path; configuring the hearing aid to operate in a closed loop manner, and adapting at least the second filter to compensate for changes in the physical feedback path.
- 14. The method of claim 13, further comprising the step of fixing the first filter after it is designed.
BACKGROUND OF THE INVENTION
[0001] This application is a continuation of copending patent application Ser. No. 09/152,033, “Feedback Cancellation Improvements,” filed Sep, 12, 1998, which is a continuation-in-part of application Ser. No. 08/972,265, “Feedback Cancellation Apparatus and Methods,” filed Nov. 18, 1997, U.S. Pat. No. 6,072,844.
Continuations (2)
|
Number |
Date |
Country |
Parent |
09152033 |
Sep 1998 |
US |
Child |
09745497 |
Dec 2000 |
US |
Parent |
08972265 |
Nov 1997 |
US |
Child |
09745497 |
Dec 2000 |
US |