Hearing Instrument Feedback Suppression via Voice-Adaptive Decorrelation
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Solution Overview
Problem
Hearing instruments face challenges in suppressing feedback noise, particularly when the user's own voice is amplified, leading to unpleasant whirring or rattling noises due to the short distances between microphones and loudspeakers, and the high sensitivity of microphones, which existing algorithms struggle to address effectively.
Innovation Solution
A method that monitors voice activity to adjust the decorrelation of the intermediate signal based on the transfer function of the closed signal loop, allowing for adaptive feedback suppression by generating a compensation signal only when necessary, thereby preventing unwanted artefacts and maintaining sound quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If frequency distortion algorithms (frequency shifting, phase modulation) are used for feedback suppression, then feedback suppression performance is improved, but audible artifacts (beats, whirring, rattling noises) are generated due to superposition with real sound signals
Solution Approach 1:
The patent applies dynamics by making the decorrelation strength adjustable based on operating conditions. The system dynamically adapts the frequency shift amount and phase modulation depth according to the estimated total amplification and voice activity detection results, optimizing feedback suppression while minimizing audible artifacts in different scenarios
Solution Approach 2:
The patent changes parameters by adjusting the frequency shift amount and phase modulation depth based on the estimated total amplification of the closed signal loop. When amplification is low, smaller frequency shifts are used to reduce artifacts; when amplification is high, larger shifts provide better feedback suppression
2Reliability
If the user's own voice is amplified through the hearing instrument, then feedback suppression is improved, but unpleasant whirring or rattling noises are generated due to superposition with bone-conducted voice signals
Solution Approach 1:
The patent uses feedback by implementing a voice activity detection mechanism that monitors the input signal and adjusts the decorrelation strength accordingly. When the user's voice is detected, the system adapts the frequency distortion parameters to minimize audible artifacts while maintaining feedback suppression effectiveness
Solution Approach 2:
The system dynamically adjusts the decorrelation strength based on voice activity detection results. During user speech, the frequency shift and phase modulation are adapted to reduce beats and unpleasant noises caused by superposition with bone-conducted voice signals, while maintaining effective feedback suppression
3Measurement precision
If high sensitivity microphones are used in hearing instruments, then sound quality is improved, but feedback noise is increased due to short distances between microphone and loudspeaker
Solution Approach 1:
The patent introduces an intermediary mechanism by implementing adaptive decorrelation with voice activity detection. This intermediary system processes the signal between the high-sensitivity microphone and the output, dynamically adjusting frequency distortion to suppress feedback noise while preserving the benefits of high microphone sensitivity
Data Source
AI summary
A method suppresses feedback in a hearing instrument. A microphone generates an input signal and a loudspeaker generates an acoustic signal which is partially fed back to the microphone via an acoustic feedback path. An intermediate signal is generated along a main signal path depending on the input signal, and an output signal is formed on the basis of the intermediate signal. A voice activity of a user is monitored, a transfer function of an electro-acoustic closed signal loop formed by the main signal path and the feedback path is estimated, that, depending on the transfer function of the closed signal loop and the voice activity of the user, the intermediate signal is decorrelated to form the output signal. A compensation signal is generated from the output signal and is fed to the input signal for feedback compensation, and the output signal is fed to the loudspeaker for reproduction.