Hearing Aid Filter Bank Phase Compensation for Zero-Delay Audio
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Solution Overview
Problem
Hearing aid systems face challenges in achieving zero delay and phase distortion, which are essential for optimal signal processing, particularly in frequency-dependent amplification, as traditional filter banks introduce significant delays and phase shifts, affecting speech intelligibility.
Innovation Solution
The method involves configuring an all-pass filter to provide the same delay as the combined processing of analysis and synthesis filter banks, with adaptive filters optimizing coefficients to ensure zero delay and phase distortion, using a variant of the normalized least-mean-square algorithm for adaptive filtering, and employing multiple delay settings in cascade to balance frequency resolution and signal processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional filter banks are used for signal processing, then frequency-dependent amplification can be achieved, but significant delays and phase shifts are introduced affecting speech intelligibility
Solution Approach 1:
The patent inverts the conventional approach by using all-pass filters to pre-compensate phase delays before the signal enters the filter bank, rather than attempting to correct delays after filtering. This allows the filter bank to operate with reduced delay while maintaining frequency resolution through adaptive filtering techniques.
Solution Approach 2:
The patent dynamically adjusts filter parameters including delay compensation values and phase correction coefficients based on the characteristics of the input signal. By changing these parameters adaptively, the system optimizes the balance between frequency resolution and processing delay for different speech and noise conditions.
2Reliability
If adaptive filtering is used to reduce delay and phase distortion, then speech intelligibility improves, but system complexity increases
Solution Approach 1:
The patent divides the signal processing into separate functional blocks: all-pass filter stage, filter bank stage, and adaptive filtering stage. Each block handles specific processing tasks with optimized complexity, allowing the system to achieve high speech intelligibility without overwhelming computational requirements in any single stage.
Solution Approach 2:
The patent introduces all-pass filters as intermediary elements that pre-compensate phase delays before the main filtering operation. These intermediaries reduce the burden on the adaptive filters, lowering overall system complexity while maintaining high speech intelligibility through coordinated multi-stage processing.
3Manufacturing precision
If all-pass filters are configured to match filter bank delay, then zero phase distortion is achieved, but device complexity increases
Solution Approach 1:
The patent implements self-adjusting mechanisms where the all-pass filter parameters are automatically configured based on the measured delay characteristics of the filter bank. This self-service approach eliminates the need for manual precision tuning while achieving zero phase distortion, reducing the practical complexity of device configuration and maintenance.
Data Source
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AI summary
A method of operating a hearing aid system with virtually zero delay and phase distortion. The invention also provides a hearing aid system (100) adapted for carrying out such a method.