Hearing Device ANC Tuning for Comb-Filtering 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, leading to degraded sound quality, waterbed effects, deviation from desired hearing targets, and variability due to gain, acoustic vent structure, and input signal level.
Innovation Solution
A method that predicts comb-filtering effects by estimating sound pressures on the ear drum from hearing processing and leakage paths, computes an ANC controller to minimize these effects, and cancels leaked sound using optimized ANC techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional ANC is used to cancel leaked direct sound, then noise reduction is achieved, but comb-filtering effects are not effectively mitigated and sound quality degrades
Solution Approach 1:
The patent changes the parameters of ANC by computing frequency-dependent transfer functions and applying frequency-specific gain adjustments. The system estimates sound pressures in different frequency ranges and computes ANC transfer functions tailored to each frequency band, rather than applying uniform noise reduction across all frequencies. This resolves the contradiction by optimizing ANC parameters to mitigate comb-filtering effects while maintaining noise reduction benefits.
Solution Approach 2:
The system dynamically adapts ANC parameters based on real-time estimation of sound pressures and comb-filtering effects. The transfer functions and gain values are computed adaptively for different frequency ranges and adjusted according to the measured acoustic conditions, allowing the ANC system to dynamically optimize between noise reduction and comb-filtering mitigation.
2Object-affected harmful factors
If ANC gain is increased to improve noise cancellation, then leaked sound is reduced, but waterbed effect increases which emphasizes comb-filtering
Solution Approach 1:
The patent applies local quality by implementing frequency-dependent ANC gain adjustment. Different frequency ranges receive different gain values and transfer function adjustments, rather than applying uniform gain across all frequencies. This allows the system to achieve effective noise cancellation in specific frequency bands while avoiding excessive gain that would cause waterbed effects in other bands, thus resolving the contradiction between noise cancellation and waterbed effect.
3Object-affected harmful factors
If ANC is optimized for noise reduction, then leaked direct sound is canceled, but deviation from desired hearing target responses occurs
Solution Approach 1:
The system applies partial action by selectively applying ANC only in frequency ranges where comb-filtering effects are detected, rather than applying uniform noise reduction across all frequencies. The patent computes the ratio of hearing processing sound pressure to leaked sound pressure and applies ANC primarily in frequency bands where this ratio indicates problematic comb-filtering, thus preserving desired hearing target responses in other frequency ranges while still achieving noise reduction where needed.
4Reliability
If hearing aid gain is increased to compensate for hearing loss, then auditory compensation is improved, but comb-filtering effects vary and degrade
Solution Approach 1:
The patent implements feedback by continuously estimating the ratio of hearing processing sound pressure to leaked sound pressure and using this information to adaptively adjust ANC parameters. The system monitors the acoustic conditions and gain settings, then computes appropriate ANC transfer functions and gain values to mitigate comb-filtering effects while maintaining effective auditory compensation. This feedback mechanism resolves the contradiction by making the system adaptive to varying gain conditions.
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 optimizing ANC controllers based on predicted sound pressures.
Implementation Method 1
active noise cancellation (ANC) techniques, which use an anti-phase signal generated by a controller configured to mitigate comb-filtering effects
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.