Hearing Aid Feedback Suppression Using Segmented Adaptive Filters
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Solution Overview
Problem
Hearing aids face challenges in effectively suppressing acoustic feedback due to the proximity of microphones and loudspeakers, which results in annoying whistling, especially under conditions with long signal propagation times and high gain requirements.
Innovation Solution
A method that estimates a first transfer function for a shorter signal response and extrapolates a second transfer function for longer delays, allowing adjustment of signal processing parameters to reduce feedback, including gain adjustments and frequency-specific feedback suppression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If adaptive filters with long length are used to suppress feedback, then feedback suppression capability is improved, but delay time increases and memory space requirements increase
Solution Approach 1:
The patent divides the feedback suppression task into two separate filters: a first adaptive filter for early signal responses and a second adaptive filter for later signal responses. This segmentation allows each filter to have optimized length, preventing the need for a single extremely long filter while maintaining comprehensive feedback suppression capability across different time delays.
Solution Approach 2:
The patent applies partial action by using two filters with different lengths suited for different time periods. The first filter handles the critical early responses with shorter length, while the second filter handles later responses, avoiding the excessive computational burden and delay of a single uniformly long filter.
2Reliability
If adaptive filters with long length are used to suppress feedback, then feedback suppression capability is improved, but memory space requirements increase
Solution Approach 1:
The patent segments the feedback suppression into two filters with different memory requirements. The first filter uses shorter memory for early responses, and the second filter uses appropriate memory for later responses, reducing the total memory space compared to a single long filter that would be needed to cover all time delays.
Solution Approach 2:
By applying partial action with two filters of optimized lengths, the patent avoids allocating excessive memory space that would be required by a single uniformly long filter, while still achieving comprehensive feedback suppression.
3Power
If high gain is used to compensate for diminished hearing capability, then hearing amplification is improved, but acoustic feedback increases
Solution Approach 1:
The patent applies preliminary action by continuously estimating the feedback path transfer function and adjusting the adaptive filters before feedback becomes problematic. This proactive approach allows the system to maintain high gain for hearing amplification while preemptively suppressing feedback signals, preventing the harmful whistling effect.
Solution Approach 2:
The patent uses feedback mechanisms by continuously monitoring the acoustic feedback path and using this information to adjust the adaptive filters. The system estimates the feedback transfer function and uses this feedback information to generate suppression signals that cancel the harmful feedback while preserving the useful hearing amplification.
Data Source
AI summary
A method and apparatus reduce feedback in a hearing aid. The method involves a first transfer function, which includes a feedback path, being estimated for a first section of a signal response. A power of a feedback signal from a second transfer function of the feedback path is estimated for a second section of the signal response, and a parameter of the signal processing device and/or of the feedback suppression unit is adjusted on the basis of the estimated power.