Hearing Device Feedback Suppression via Frequency Shifting
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Solution Overview
Problem
Hearing devices experience annoying feedback whistling due to acoustic feedback, which is exacerbated by high correlation between useful and feedback signals, leading to artifacts and disruptive signal distortions, especially in the low-frequency range, where human hearing is sensitive, and existing adaptive feedback suppression methods fail to effectively suppress these issues.
Innovation Solution
A hearing device with an adaptive feedback suppression unit, low-pass and high-pass filters, and a frequency shifting unit that separates and shifts high-frequency components by 10-30 Hz, reducing overlapping signal components and minimizing disruptive artifacts by creating a gap between filter cut-off frequencies, using Cauer filters for enhanced edge steepness and reduced signal distortions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If frequency shifting is applied to suppress feedback, then feedback suppression is improved, but signal distortions and artifacts increase
Solution Approach 1:
The patent segments the frequency spectrum by introducing a frequency gap between low-pass and high-pass filter cut-off frequencies. This segmentation prevents overlapping of shifted and unshifted signal components, thereby reducing artifacts while maintaining feedback suppression effectiveness.
Solution Approach 2:
The patent applies different filter characteristics (Cauer filters with enhanced edge steepness) to specific frequency regions. By optimizing filter properties locally in the frequency domain, the patent achieves better suppression of feedback artifacts while preserving signal quality in critical frequency ranges.
2Reliability
If adaptive compensation filter is used for feedback suppression, then feedback cancellation is improved, but incorrect adaptations occur due to high correlation between useful signal and feedback signal
Solution Approach 1:
The patent extracts the feedback signal component from the total microphone signal by using a separate adaptive compensation filter that processes only the earpiece signal. This extracted feedback component is then subtracted from the microphone signal, avoiding the correlation problem that arises when trying to separate feedback from the combined signal.
Solution Approach 2:
The patent introduces an intermediary adaptive compensation filter that acts as a mediator between the earpiece signal and the microphone signal. This intermediary structure allows feedback suppression without directly correlating the useful signal and feedback signal, thereby preventing incorrect adaptations.
3Object-affected harmful factors
If only high frequencies are shifted to avoid low frequency distortions, then sensitivity to distortions is reduced, but audible detuning of useful signal occurs
Solution Approach 1:
The patent applies dynamic frequency shifting only to the high-pass filtered signal component, while leaving the low-pass filtered signal component at its original frequency. This dynamic approach adapts the frequency shifting operation to the specific frequency content being processed, avoiding detuning artifacts while maintaining distortion reduction benefits.
Data Source
AI summary
A hearing device has a feedback suppression unit. The hearing device further has a low-pass filter characterized by a first cut-off frequency, which couples out a low-frequency signal component from an output signal of the hearing device, and a high-pass filter characterized by a second cut-off frequency, which couples out a high-frequency signal component from the output signal of the hearing device. A frequency shift unit shifts the frequency of the high-frequency signal component to higher frequencies. A gap exists between the first and the second cut-off frequency. As a result of the different limit frequencies, signal distortions caused by frequency shifts are effectively suppressed. Feedback is suppressed continuously and rapidly at higher frequencies.