Adaptive Feedback Canceler for Hearing Devices
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Solution Overview
Problem
Existing feedback cancellation systems in hearing devices struggle to differentiate between tonal inputs and feedback signals, leading to unwanted artifacts such as squealing or whistling, especially when the feedback path changes, and fail to adapt quickly enough to minimize the duration and loudness of these artifacts.
Innovation Solution
A method is introduced that detects feedback path changes by estimating a product of subband error and output signals, calculating a metric based on this product, and adjusting the adaptation rate of the adaptive feedback canceler. When a feedback path change is detected, a faster adaptation rate is applied to quickly adapt the filter and cancel the feedback, while a slower rate is maintained when no change is detected to prevent entrainment artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a fast adaptation rate is applied to quickly track feedback path changes, then feedback cancellation speed is improved, but entrainment artifacts occur when tonal inputs are present
Solution Approach 1:
The patent applies dynamics by making the adaptation rate variable rather than fixed. The system dynamically adjusts the adaptation rate based on the detected signal characteristics - using fast adaptation when feedback path changes are detected and slow adaptation when tonal inputs are present. This resolves the contradiction by allowing the system to have both fast response capability and artifact suppression depending on the operational context.
Solution Approach 2:
The patent changes the parameter of adaptation rate from a static value to a dynamic value that varies based on signal analysis. By monitoring the product of subband error and output signals, the system detects feedback path changes and adjusts the adaptation rate parameter accordingly. This parameter change enables the system to achieve fast cancellation when needed while preventing entrainment artifacts during tonal input.
2Object-generated harmful factors
If a slow adaptation rate is applied to prevent entrainment artifacts, then signal quality is improved, but feedback path changes are not tracked quickly enough
Solution Approach 1:
The system dynamically adjusts the adaptation rate based on real-time detection of feedback path changes. When changes are detected through analysis of the product of subband error and output signals, the system switches to fast adaptation mode to maintain effective feedback cancellation. When no changes are detected, it uses slow adaptation to prevent artifacts, thus maintaining both reliability and signal quality.
Solution Approach 2:
The patent implements a feedback mechanism where the system continuously monitors the product of subband error and output signals to detect feedback path changes. This feedback information is then used to adjust the adaptation rate, creating a closed-loop control system that automatically responds to changing conditions and maintains optimal performance.
3Reliability
If adaptive feedback cancellation is applied continuously, then feedback is cancelled effectively, but computational complexity and processing load increase
Solution Approach 1:
The patent applies partial action by using subband processing - dividing the full bandwidth signal into multiple subbands and processing each separately. This allows the system to focus computational effort on specific frequency regions where feedback is most likely to occur, reducing overall processing complexity while maintaining effective feedback cancellation. The system applies adaptation only when and where needed rather than continuously across the entire spectrum.
Data Source
AI summary
Methods and systems for signal processing an audio signal in a hearing device to detect when feedback path change occurs and controlling an adaptive feedback canceler to remove the feedback are provided. The hearing device includes a receiver and a microphone. An exemplary method includes detecting whether a tonal signal is caused by a feedback path change by estimating a product of a subband error signal and a subband output signal generated in response to a subband audio input signal; estimating a fast metric based on the estimated product and estimating a slow metric; and applying or maintaining an adaptation rate to the adaptive feedback canceler of the hearing device, wherein the adaptation rate applied or maintained is selected based upon a value of the difference between the fast and slow metrics compared to a threshold value.