Dual Adaptive Filter Feedback Suppression in Hearing Aids
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Solution Overview
Problem
Existing hearing aid feedback suppression methods require additional fitting steps and fail to capture true invariant parts of the feedback path, leading to instability and audible distortions due to the need for initial filter initialization and inability to adapt to slow changes in the feedback path.
Innovation Solution
A hearing aid with a feedback suppression circuit comprising a slow adaptive filter and a fast adaptive filter, where the slow adaptive filter eliminates the need for initial filter initialization and adapts to slow changes in the feedback path, such as ear wax accumulation or component drift, while the fast adaptive filter handles rapid changes like chewing or sneezing, without requiring separate probe signals or additional fitting steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single adaptive filter is used for feedback suppression, then the filter can adapt to changes in the feedback path, but the filter is slow and/or inaccurate in tracking both slow and rapid changes
Solution Approach 1:
The patent divides the feedback suppression system into two separate adaptive filters: a slow adaptive filter that tracks slow changes in the feedback path (such as component drift or ear canal changes) and a fast adaptive filter that tracks rapid changes (such as chewing or sneezing). This segmentation allows each filter to be optimized for its specific time scale, resolving the contradiction between tracking accuracy and adaptation speed.
2Ease of operation
If filter coefficients are initialized during fitting or power-up, then the feedback suppression circuit can start operation, but additional fitting steps are required and true invariant parts of the feedback path are not captured
Solution Approach 1:
The slow adaptive filter automatically adapts to slow changes in the feedback path during normal operation without requiring manual initialization or additional fitting steps. The filter continuously updates its coefficients based on the error signal, enabling the system to self-correct and capture true invariant parts of the feedback path over time, eliminating the need for separate initialization procedures.
3Reliability
If the feedback gain is lowered to stop feedback, then feedback instability is reduced, but the maximum gain that can be used is limited
Solution Approach 1:
The patent employs feedback suppression by modeling the feedback path and subtracting the modeled feedback signal from the microphone signal. This active feedback cancellation allows the hearing aid to maintain high amplifier gain for improved audibility while simultaneously suppressing feedback instability, resolving the contradiction between gain and stability.
Data Source
AI summary
A new method for performing adaptive feedback suppression in a hearing aid and a hearing aid utilizing the method are provided. According to the method, a slow adaptive filter and a fast adaptive filter with different error signals for filter coefficient updating are used for feedback suppression.