Binaural Hearing Aid Compression for Stable Spatial Sound
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Solution Overview
Problem
Traditional hearing aids with audio compression suffer from issues like compression distortion, pumping, poor protection against sudden loud sounds, and reduced speech intelligibility due to inadequate selection of compression parameters, and multi-channel compression reduces spectral and temporal contrast, affecting sound quality and intelligibility.
Innovation Solution
A hearing aid system with a binaural communication link that transmits and combines level estimates from fast and slow acting level estimators between two hearing aids, allowing for synchronized automatic volume control, independent gain estimations in multiple frequency bands, and combining slow and fast compression systems for improved sound processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If fast-acting compression is used with short time constants for attack and release, then compression response speed is improved, but compression distortion increases and sound quality deteriorates due to squeezing of the dynamic range
Solution Approach 1:
The patent divides the compression system into multiple parallel compression channels, each with different time constants. Fast compression channels handle transient peaks while slow compression channels maintain overall dynamic range, preventing the squeezing distortion that occurs in single-channel fast compression.
Solution Approach 2:
The system dynamically switches between fast and slow compression channels based on signal characteristics. Fast channels are activated for transient sounds requiring immediate response, while slow channels handle sustained signals to preserve natural dynamic range and sound quality.
2Reliability
If slow release time constants are used in compression, then protection against sudden loud sounds is improved, but pumping effect occurs where softer sounds are suppressed following loud sounds
Solution Approach 1:
The patent segments the compression function into parallel channels with different release time constants. Slow-release channels provide protection against sudden loud sounds, while fast-release channels quickly restore gain for softer sounds, eliminating the pumping effect caused by uniform slow release.
Solution Approach 2:
The system changes the release time constant parameter dynamically based on signal level and channel characteristics. Different channels use different release time constants simultaneously, allowing the system to achieve both protection against loud sounds and avoidance of pumping effects.
3Object-generated harmful factors
If multi-channel compression is applied in separate frequency bands, then interaction between different signals at different frequencies is reduced, but spectral contrast is reduced which may reduce speech intelligibility
Solution Approach 1:
The patent applies different compression characteristics to different frequency channels based on local signal characteristics. Each frequency band is processed independently with tailored compression parameters, reducing harmful interactions while preserving spectral contrast through localized processing.
Solution Approach 2:
The system dynamically adjusts compression parameters in each frequency band based on real-time signal analysis. This allows the system to reduce signal interaction where needed while maintaining spectral contrast in frequency regions critical for speech intelligibility.
4Manufacturing precision
If compression is applied to normalize dynamic range, then recruitment is compensated and listening situations are adjusted, but temporal contrast in the signal is reduced which may reduce speech intelligibility
Solution Approach 1:
The patent segments temporal processing into multiple time scales using parallel compression channels with different attack and release time constants. Fast channels preserve temporal contrast for speech cues, while slow channels provide overall dynamic range normalization, preventing loss of intelligibility information.
Solution Approach 2:
The system dynamically selects which compression channels to activate based on temporal signal characteristics. When rapid level changes occur, fast channels are emphasized to preserve temporal contrast, while during steady-state signals, slow channels provide normalization without affecting intelligibility.
Data Source
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AI summary
A hearing aid comprises an audio signal input device (11), a signal processor (12) and a signal output device (13) which presents a processed audio signal perceivable as sound to an ear of a user. The signal processor (12) comprises fast acting level estimators (4.8) and slow acting level estimators (4.7). A communication link between two hearing aids at each ear of a user allows the transmission between the two hearing aids of level estimates from the slow acting level estimators (4.7).