Hearing Aid Band Split Compressor Gain Control
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Solution Overview
Problem
Existing hearing aid technologies face challenges in providing effective frequency-dependent amplification and compression, leading to spectral smearing that affects speech intelligibility, especially when using multi-band non-linear processing.
Innovation Solution
The method involves filtering input sound signals into frequency bands, estimating signal levels, grouping bands, calculating compressor input levels based on signal levels from multiple bands, and determining compressor gains to avoid spectral smearing while maintaining individual gain adjustments for each band.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the number of frequency bands is increased to provide detailed frequency-dependent compensation, then the frequency-dependent amplification and compression capability is improved, but spectral smearing occurs that causes loss of speech intelligibility
Solution Approach 1:
The input sound signal is divided into multiple frequency bands using band split filters, allowing independent gain adjustment for each frequency band to compensate for frequency-dependent hearing losses while maintaining speech intelligibility through controlled processing
Solution Approach 2:
The patent applies compression processing selectively based on signal level thresholds. Gain constraint is applied only when the signal level exceeds a predetermined threshold, allowing full gain adjustment for low-level signals while preventing spectral smearing for high-level signals
2Loss of information
If gain constraint is applied to preserve spectrum contrast at high levels, then speech intelligibility is improved, but the capability to cope with spectral smearing at all signal levels is reduced
Solution Approach 1:
The gain constraint threshold is made adaptive based on the estimated signal level in each frequency band. The threshold is set as a proportion of the estimated signal level, allowing the system to dynamically adjust between preserving spectrum contrast and preventing spectral smearing depending on the current signal conditions
Data Source
AI summary
In a method and hearing aid (200) for processing sound signals for hearing impaired persons by providing multi-band compression processing an input sound signal is filtered by a band split filter (202) into a number of frequency bands to obtain band split signals. A signal level for each of the band split signals is determined and the frequency bands are arranged into a number of groups. Based on the signal levels in each of the groups, a compressor input level for a number of band split compressors each associated to one of the frequency bands is calculated. A compressor gain for each band split compressor is determined based on the corresponding compressor input signal and the band split signals are amplified with the corresponding compressor gain and summed in a summing unit (208) to produce an output sound signal.