Transparent Hearing Aid Signal Processing for Artifact Reduction
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Solution Overview
Problem
Hearing aids often introduce artifacts such as comb filtering and phase distortion due to latency and phase-dependent gain, which affect the natural perception of sound, especially in individuals with hearing loss, and fail to completely address the unique insertion effects caused by varying ear shapes.
Innovation Solution
A hearing aid with a signal processor featuring both level-dependent and level-independent filter sections, providing separate electronic paths to correct for hearing loss and earpiece insertion effects, ensuring a 'natural' or 'transparent' sound perception by amplifying low-level sounds and reducing gain at higher levels, thus minimizing artifacts and preserving natural cues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If level-dependent gain is used to amplify low-level sounds, then hearing loss compensation is improved, but artifacts such as comb filtering and phase distortion are introduced
Solution Approach 1:
The signal processing is divided into two separate parallel paths: a level-dependent path for amplifying low-level sounds and a level-independent path for preserving natural sound cues. This segmentation allows each path to perform its specific function without introducing artifacts that would compromise overall sound quality.
Solution Approach 2:
Different processing characteristics are applied to different portions of the audio signal based on its level. Low-level sounds receive level-dependent gain with hearing loss compensation, while high-level sounds pass through the level-independent path to maintain natural perception. This local quality approach ensures artifact-free processing where needed.
2Power
If closed earpiece is used to block ear canal, then gain before feedback is improved, but occlusion effect and natural sound perception are worsened
Solution Approach 1:
The patent combines the benefits of closed earpiece (high gain before feedback) with the advantages of open earpiece (natural sound perception) by merging two signal paths. The level-independent path preserves natural ear canal acoustics while the level-dependent path provides necessary amplification, effectively merging the advantages of both earpiece types.
Solution Approach 2:
The level-independent path acts as an intermediary that preserves natural sound cues and ear canal acoustics, mediating between the closed earpiece structure and the user's natural hearing perception. This intermediary path prevents the occlusion effect by maintaining an open acoustic pathway for high-level sounds.
3Measurement precision
If custom molded earpieces are used to account for individual ear shapes, then insertion effect compensation is improved, but device complexity and fitting process are increased
Solution Approach 1:
Instead of physically customizing the earpiece for each user, the patent changes the signal processing parameters dynamically. The level-dependent and level-independent paths use adjustable gain and filtering parameters that can be programmed to compensate for individual ear canal characteristics without requiring custom physical molds.
Solution Approach 2:
The patent replaces the mechanical customization approach (custom molded earpieces) with an electronic signal processing system. The level-independent path with its adjustable parameters provides insertion effect compensation through electronic means, eliminating the need for complex custom molding and manual fitting processes.
Data Source
AI summary
The hearing aid includes a signal processor having a level-dependent filter section and a level-independent filter section. The level-dependent filter section provides level-dependent gain wherein sound is attenuated or amplified depending on the level of the incoming sound. The level-independent filter section provides substantially constant gain wherein sound that passes through the filter section is not changed in level, and provides transparency in that it corrects for insertion loss caused by the earpiece of the hearing aid when worn by the user. The level dependent and level independent filter sections, when fitted to the user, greatly improve the user's perception of sound.