Hearing Aid Feedback Cancellation via Frequency Warping
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Solution Overview
Problem
Acoustic feedback in hearing aids, particularly in behind-the-ear receiver in the canal systems, causes instability and 'howling' artifacts due to significant acoustic coupling between microphones and loudspeakers, which existing adaptive feedback cancellation methods struggle to fully address.
Innovation Solution
The implementation of frequency warping, using all-pass filters, to break the Nyquist stability criterion in both amplitude and phase domains, combined with Least Mean Square (LMS) based adaptive feedback cancellation, improves stability and reduces feedback artifacts without introducing howling side effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If adaptive feedback cancellation (AFC) is used to reduce acoustic feedback, then feedback artifacts are reduced, but the system may still become unstable and produce howling artifacts when acoustic coupling conditions are favorable
Solution Approach 1:
The patent applies frequency warping by changing the frequency parameter of the audio signal through all-pass filters. This warps the frequency spectrum to break the Nyquist stability criterion, making the system more resistant to acoustic feedback instability while maintaining feedback cancellation performance
Solution Approach 2:
The patent introduces an intermediary frequency warping module between the audio signal and the AFC processor. This intermediary layer processes the signal through all-pass filters to apply frequency warping, which then feeds into the AFC system to achieve both stability and feedback reduction
2Reliability
If frequency warping is applied to break the Nyquist stability criterion, then system stability is improved, but audio signal distortions are introduced
Solution Approach 1:
The patent changes the frequency parameter through all-pass filters to achieve frequency warping. This parameter transformation breaks the Nyquist stability criterion and improves system stability while introducing controlled distortions that are acceptable for the application
Solution Approach 2:
The patent applies frequency warping selectively to specific frequency bands rather than the entire spectrum. By targeting specific bands where acoustic feedback is most likely to occur, the system achieves stability improvement with minimal impact on overall audio quality
Data Source
AI summary
A method and system or device such as a hearing aid are provided for processing audio signals. In accordance with the method, an audio signal is received and divided into a plurality of frequency sub-bands. For each of the frequency sub-band signals, the signal is further divided into overlapping temporal frames. Each of the temporal frames are windowed. Frequency warping is performed on each of the windowed frames. Overlap-and-add is performed on the frequency warped frames. The frequency warped sub-bands are combined into a full band to provide a frequency warped signal.