Hearing Device ANC for Frequency-Selective Comb-Filter Control
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Solution Overview
Problem
Conventional active noise cancellation (ANC) methods for hearing devices are not optimized to mitigate comb-filtering effects, often leading to waterbed effects, deviation from desired hearing targets, and variability based on gain, vent structure, and input signal levels, which degrade sound quality.
Innovation Solution
A method that predicts comb-filtering effects by estimating sound pressures from hearing processing and leakage paths, and computes an ANC controller to cancel leaked sound, optimizing ANC performance in specific frequency ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional ANC is applied to cancel leaked direct sound, then noise reduction is achieved, but comb-filtering effects are not effectively mitigated and sound quality deteriorates due to waterbed effects
Solution Approach 1:
The patent applies parameter changes by modifying the ANC filter coefficients based on predicted comb-filtering characteristics. The system dynamically adjusts ANC parameters (filter order, coefficients, frequency ranges) according to the estimated ratio of hearing processing sound to leaked sound, thereby optimizing cancellation effectiveness while avoiding waterbed effects that degrade sound quality.
Solution Approach 2:
The patent implements feedback by using the predicted comb-filtering effect information to continuously adapt the ANC controller. The system estimates the ratio of hearing processing sound to leaked direct sound, predicts comb-filtering characteristics, and uses this feedback to adjust ANC filter coefficients in real-time, creating a closed-loop system that optimizes noise cancellation while preserving sound quality.
2Object-affected harmful factors
If ANC is used to reduce leaked sound, then noise cancellation improves, but the cancellation response deviates from desired hearing target responses
Solution Approach 1:
The patent applies local quality by implementing frequency-selective ANC cancellation. Instead of uniformly canceling leaked sound across all frequencies, the system identifies specific frequency ranges where comb-filtering occurs and applies ANC only in those regions. This localized approach preserves the desired hearing target responses in frequencies where ANC is not applied, while effectively mitigating comb-filtering in problematic frequency ranges.
3Object-affected harmful factors
If ANC gain is increased to improve cancellation, then leaked sound reduction improves, but waterbed effect increases which emphasizes comb-filtering
Solution Approach 1:
The patent applies partial action by implementing selective ANC cancellation only in frequency ranges where comb-filtering is predicted to occur, rather than applying full-strength ANC across the entire frequency spectrum. The system estimates the ratio of hearing processing sound to leaked sound and applies ANC proportionally, using stronger cancellation where needed and weaker or no cancellation where it would create waterbed effects, thereby achieving effective comb-filtering mitigation without excessive ANC gain.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Effectively reduces comb-filtering effects without sacrificing low-frequency hearing aid sound, improving sound quality and wearer comfort by integrating ANC with hearing aid processing.
Implementation Method 1
cancel leaked sound into an ear canal of the wearer for the hearing device in the one or more frequency ranges using the ANC controller
Data Source
AI summary
Disclosed herein, among other things, are systems and methods for active noise cancellation (ANC) for hearing device applications. A method includes estimating a first sound pressure on an ear drum of a wearer of the hearing device caused by a hearing processing signal, estimating a second sound pressure on the ear drum of the wearer of the hearing device caused by a leakage path of the hearing device, and computing a ratio of the first sound pressure and the second sound pressure to predict a comb-filtering effect for the hearing device. The method also includes computing an ANC controller using the computed ratio in one or more frequency ranges, and canceling leaked sound into an ear canal of the wearer for the hearing device in the one or more frequency ranges using the ANC controller.