ITE Hearing Aid Gain Control for Comb-Filter Suppression
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Solution Overview
Problem
Comb-filter artefacts occur in hearing devices due to the mixing of directly propagated sound from the environment with processed sound, particularly in acoustic environments with broadband sound components, leading to significant issues at lower frequencies affecting normal speech elements.
Innovation Solution
A hearing aid with an ITE-part located in the ear canal, featuring a correlator to determine the correlation between input signals from the environment and the eardrum, and a gain modifier to adjust gain based on this correlation, suppressing comb-filter effects in critical frequency ranges using a comb filter effect gain modification estimator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If processing delay is reduced to less than 10 ms, then real-time performance is improved, but comb-filter artefacts worsen at lower frequencies
Solution Approach 1:
The patent uses the comb-filter effect itself to detect and correct the problem. By analyzing the correlation between microphone input and ear canal sensor output, the system identifies comb-filter artefacts and applies gain modification to suppress them, thereby converting the harmful effect into a useful detection mechanism
Solution Approach 2:
The patent dynamically adjusts the gain parameter in the frequency domain based on detected comb-filter characteristics. By modifying gain values at specific frequencies where comb-filter artefacts occur, the system eliminates the harmful effect while maintaining the low processing delay
2Measurement precision
If gain is increased to compensate for hearing impairment, then speech intelligibility is improved, but comb-filter artefacts are amplified
Solution Approach 1:
The patent applies different gain modifications to different frequency regions. By identifying specific frequency ranges where comb-filter artefacts occur and applying targeted gain adjustments only in those regions, the system maintains speech intelligibility while suppressing artefacts locally without affecting other frequency ranges
Solution Approach 2:
The system dynamically modifies gain parameters based on the detected correlation between input signals and ear canal responses. By adjusting gain values in response to real-time conditions, the system optimizes speech intelligibility while minimizing comb-filter artefact amplification
3Measurement precision
If broadband noise suppression is activated, then signal-to-noise ratio is improved, but natural sound quality deteriorates
Solution Approach 1:
The patent applies noise suppression selectively in the frequency domain, targeting specific frequency ranges where comb-filter artefacts and broadband noise occur. By preserving frequencies that contribute to natural sound quality while suppressing problematic frequencies, the system improves signal-to-noise ratio without degrading overall naturalness
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-filter artefacts by dynamically adjusting gain in response to acoustic environments, improving sound quality and clarity, especially in the presence of broadband noise.
Implementation Method 1
at least one second input transducer providing at least one second electric input signal representing said sound as received at the at least one second input transducer, the at least one second input transducer being located in said ITE-part to pick up sound at the eardrum of the user
Implementation Method 2
at least one first input transducer providing at least one first electric input signal representing said sound as received at the respective at least one first input transducer (e.g. a microphone)
Implementation Method 3
an output transducer for providing stimuli perceivable as sound to the user in dependence of said processed signal
Implementation Method 4
a correlator configured to determine a correlation measure between the at least one second electric input signal, or a signal originating therefrom, and a signal of the forward path
Data Source
AI summary
A hearing aid comprises a) an ITE-part adapted for being located at or in an ear canal of the user, b) a forward path for processing sound from the environment of the user. The forward path comprises b1) at least one first input transducer providing at least one first electric input signal representing said sound as received at the respective at least one first microphone, said at least one first input transducer being located to allow picking up sound from the environment of the user, b2) an audio signal processor comprising a gain unit for applying a frequency and/or level dependent prescribed gain to compensate for a hearing impairment of the user to said at least one first electric input signal, or a signal or signals originating therefrom, and configured to provide a processed signal in dependence thereof, b3) an output transducer for providing stimuli perceivable as sound to the user in dependence of said processed signal. The hearing aid further comprises c) at least one second input transducer providing at least one second electric input signal representing said sound as received at the at least one second input transducer, the at least one second input transducer being located in said ITE-part to pick up sound at the eardrum of the user, d) a correlator configured to determine a correlation measure between the at least one second electric input signal, or a signal originating therefrom, and a signal of the forward path and e) a gain modifier configured to modify said gain of the gain unit in dependence of said correlation measure. A method of operating a hearing aid is further disclosed.