Hearing Device Filter Bank with Frequency-Dependent Attenuation
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Solution Overview
Problem
Conventional filter banks in hearing aids suffer from high circuit complexity and group delay, leading to fluctuations in signal quality and signal-to-noise ratio due to inadequate consideration of oversampling and signal manipulation, particularly in high-frequency amplification for hearing loss compensation.
Innovation Solution
A filter bank system with analysis and synthesis filter banks featuring separately configurable frequency-independent and frequency-dependent attenuation components, optimized to reduce filter order and group delay, and incorporating masking effects and periodic modifications based on oversampling factors to maintain consistent signal-to-noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional filter banks are used in hearing aids, then signal processing can be performed, but circuit complexity and group delay become excessively high
Solution Approach 1:
The filter bank is divided into multiple sub-bands, with each sub-band processed by dedicated filter structures. This segmentation allows independent optimization of each sub-band's attenuation characteristics, reducing overall circuit complexity while maintaining signal quality consistency across all bands
Solution Approach 2:
Different attenuation characteristics are applied to different frequency regions. The analysis filter bank uses frequency-independent attenuation in stop-bands while the synthesis filter bank uses frequency-dependent attenuation, matching the local requirements of each frequency region to minimize overall complexity
2Adaptability or versatility
If high amplification is applied to compensate for hearing loss, then hearing impairment is addressed, but aliasing and imaging disturbances increase
Solution Approach 1:
The patent converts the harmful aliasing and imaging effects into beneficial structures by designing the synthesis filter bank to deliberately generate matching aliasing and imaging components that cancel the harmful ones from the analysis stage, thereby eliminating disturbances while maintaining high amplification capability
Solution Approach 2:
The analysis and synthesis filter banks are designed with asymmetric characteristics - the analysis bank uses frequency-independent stop-band attenuation while the synthesis bank uses frequency-dependent attenuation. This asymmetry allows optimal cancellation of aliasing and imaging effects across different frequency regions
3Object-affected harmful factors
If filter order is increased to reduce aliasing and imaging, then disturbance cancellation improves, but group delay increases beyond acceptable limits
Solution Approach 1:
The patent changes the attenuation parameters differently for analysis and synthesis filter banks. By using frequency-independent attenuation in the analysis bank and frequency-dependent attenuation in the synthesis bank, effective aliasing cancellation is achieved with lower filter orders, thereby reducing group delay to acceptable levels
Data Source
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AI summary
The filter bank system has an analysis filter bank for analyzing the input signals in partial band signal. A stop-band attenuation (12) assembles one of a transmission function of analysis filter bank from a separately configured, frequency dependent analysis-base attenuation fraction and separately configured, frequency dependent analysis attenuation fractions (10,11). A synthesis filter bank is provided for assembling a manipulated partial band signal with another partial band signal.