Hearing Aid Filter Bank Phase Correction for Group Delay Control
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Solution Overview
Problem
The existing filter bank configurations in hearing aids cause perceivable distortions due to significant deviations in group delay at transitions between channels, leading to unwanted time offsets of spectral components in the output signal.
Innovation Solution
A filter bank configuration that includes an analysis filter bank and a synthesis filter bank with coupled filters, where means are provided to change the phase of signals in at least one channel to reduce the difference between the group delay and a prescribable reference value, using a scaling apparatus with complex factors to minimize deviations in group delay across frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a filter bank configuration with multiple channels is used for spectral decomposition, then frequency-dependent amplification is enabled, but group delay deviations cause perceivable distortions at channel transitions
Solution Approach 1:
The patent applies parameter changes by adjusting the phase response of individual filters in the analysis and synthesis filter banks. Specifically, the phase of filters is modified to compensate for group delay deviations at channel transitions, while maintaining the amplitude response characteristics. This allows the filter bank to achieve both frequency-dependent amplification capability and consistent group delay across all channels, resolving the technical contradiction between adaptability and precision.
2Manufacturing precision
If phase adjustment means are added to reduce group delay deviations, then signal distortion is reduced, but device complexity increases
Solution Approach 1:
The patent merges the phase adjustment function with the existing filter bank structure by integrating phase correction filters into the analysis and synthesis filter banks. Instead of adding separate phase adjustment stages, the phase modification is incorporated directly into the filter design, allowing group delay compensation to be achieved within the existing signal processing framework. This reduces the overall device complexity while maintaining signal quality improvements.
Data Source
AI summary
A filter bank configuration for a hearing device has filters in an analysis filter bank and corresponding filters in a synthesis filter bank that are coupled pair-wise to form a channel in each case. In order to compensate for a hearing loss, sub-band signals are amplified in the individual channels with the aid of multipliers. In the process, an audible distortion of an output signal Y of the filter bank configuration as a result of differences between amplification factors of the multipliers of neighboring channels should be prevented. Here, at least one channel changes a phase of a sub-band signal transmitted by the channel such that a difference between a group delay of the filter bank configuration and a prescribable reference value is reduced for at least one predetermined frequency. The filter bank configuration is particularly suited to hearing aids.