Adaptive Residual Feedback Suppression in Hearing Aids
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Solution Overview
Problem
Hearing aids face limitations in maximum gain due to residual feedback, which cannot be completely eliminated by existing feedback suppression methods, leading to audible distortions and instability.
Innovation Solution
A new method for adaptive feedback suppression in hearing aids, where residual feedback is estimated and reduced by adjusting gain based on the input signal's power spectrum, using a feedback suppression circuit with adaptive filters and a gain processor to compensate for residual feedback signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If feedback suppression circuit is used to model and subtract feedback path, then feedback signal is reduced, but residual feedback remains causing output level to exceed desired level near instability
Solution Approach 1:
The patent implements a gain processor that continuously monitors the feedback compensated audio signal and dynamically adjusts the gain applied to the hearing aid output. This feedback mechanism detects residual feedback levels and modifies the gain accordingly, creating a closed-loop control system that adapts to changing feedback conditions and prevents output level excursions.
Solution Approach 2:
The patent transitions from a static feedback suppression approach to a dynamic system where the gain processor continuously adapts the gain based on real-time signal characteristics. The system dynamically adjusts parameters such as attack and release times, gain reduction amounts, and frequency-dependent gain adjustments to optimize performance under varying acoustic conditions.
2Power
If gain is increased to improve audibility, then hearing aid output level increases, but feedback loop becomes unstable causing audible distortions or howling
Solution Approach 1:
The patent applies gain reduction proactively before feedback instability occurs. The gain processor continuously monitors signal levels and feedback characteristics, and reduces gain in advance when conditions suggest approaching instability. This preliminary action prevents feedback howling and distortions before they manifest, allowing the system to operate at higher gains safely.
Solution Approach 2:
The gain processor uses feedback from the microphone signal and feedback path model to continuously adjust the output gain. This closed-loop control enables the system to maintain stability even at high gain settings by dynamically compensating for feedback effects in real-time.
Data Source
AI summary
A hearing aid includes: an input transducer for generating an audio signal; a feedback suppression circuit configured for modelling a feedback path of the hearing aid; a subtractor for subtracting an output signal of the feedback suppression circuit from the audio signal to form a feedback compensated audio signal; a signal processor that is coupled to an output of the subtractor for processing the feedback compensated audio signal to perform hearing loss compensation; and a receiver that is coupled to an output of the signal processor for converting the processed feedback compensated audio signal into a sound signal; wherein the hearing aid further comprises a gain processor for performing gain adjustment of the feedback compensated audio signal based at least on an estimate of a residual feedback signal of the feedback compensated audio signal, wherein the estimate of the residual feedback signal is based at least on the audio signal.