Variable Compression Hearing Aid Signal Processing
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Solution Overview
Problem
Current multichannel wide dynamic-range compression (WDRC) hearing aids face challenges in balancing audibility and distortion, as they either maximize audibility with high distortion or minimize distortion at the cost of reduced audibility, and often compress the entire auditory dynamic range rather than the speech dynamic range, which can lead to suboptimal intelligibility and quality.
Innovation Solution
A new hearing aid method that varies amplification in response to signal characteristics, using a compressor with a variable input/output rule based on hearing loss and signal level, employing peak and valley detectors to adjust gain values, and minimizing compression to maintain audibility while reducing distortion, thereby fitting the speech dynamic range to the impaired ear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If fast compression with many narrow frequency channels is used, then audibility is maximized, but distortion increases
Solution Approach 1:
The patent applies dynamics by making the compression ratio variable rather than fixed. The system adapts the compression ratio based on the input signal level, using faster compression ratios for low-level signals to improve audibility and slower compression ratios for high-level signals to reduce distortion. This dynamic adjustment resolves the contradiction between maximizing audibility and minimizing distortion.
Solution Approach 2:
The patent changes the compression ratio parameter based on signal level. Different compression ratios are applied depending on whether the signal is below, at, or above the threshold level. This parameter change allows the system to optimize both audibility and distortion reduction under different operating conditions.
2Object-generated harmful factors
If slow compression is used, then distortion is minimized, but audibility is reduced
Solution Approach 1:
The system dynamically selects compression ratios based on signal level. For low-level signals below the threshold, a fast compression ratio is used to maximize audibility. For high-level signals above the threshold, a slow compression ratio is used to minimize distortion. This dynamic behavior resolves the contradiction between distortion minimization and audibility maintenance.
3Measurement precision
If compression amplification is applied, then speech above impaired threshold is improved, but speech envelope distortion increases
Solution Approach 1:
The patent changes the compression ratio parameter based on the relationship between input signal level and threshold level. When the input signal is below the threshold, a compression ratio of 1:1 (no compression) is used to preserve envelope integrity. When the input signal is above the threshold, compression is applied to improve speech intelligibility. This conditional parameter change resolves the contradiction between improving speech above threshold and preserving envelope distortion.
4Object-generated harmful factors
If linear amplification is used, then speech quality is maintained, but audibility is reduced for low signal levels
Solution Approach 1:
The patent changes the amplification strategy based on signal level relative to threshold. For signals below the threshold, compression amplification is applied to improve audibility. For signals at or above the threshold, linear amplification is used to maintain speech quality. This conditional parameter change resolves the contradiction between maintaining speech quality and improving audibility for low signal levels.
Data Source
AI summary
A hearing aid includes a microphone for conversion of acoustic sound into an input audio signal, a signal processor for processing the input audio signal for generation of an output audio signal; and a transducer for conversion of the output audio signal into a signal to be received by a human, wherein the signal processor includes a compressor with a compressor input/output rule that is variable in response to a signal level of the input audio signal.