Adaptive Filter Maximum Stable Gain Measurement
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Solution Overview
Problem
Current systems for measuring maximum stable gain in hearing assistance devices, such as hearing aids, are inadequate in accurately determining the gain before acoustic feedback occurs, which is crucial for optimal programming and user experience.
Innovation Solution
The system employs adaptive filtering techniques, including LMS, NLMS, FIR, and Wiener filters with variable step sizes, to calculate maximum stable gain as a function of frequency by injecting noise into the hearing assistance device's processing channel and using adaptive filters to cancel acoustic feedback, allowing for precise determination of gain limits across different frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If adaptive filtering techniques are used to measure maximum stable gain, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent uses a virtual acoustic feedback canceller that copies the feedback path characteristics through adaptive filtering. Instead of physically measuring the complex feedback loop directly, the system creates a mathematical model (copy) of the feedback path using the adaptive filter coefficients, thereby simplifying the measurement process while maintaining precision.
Solution Approach 2:
The patent replaces direct physical measurement of acoustic feedback with signal processing techniques. By substituting the mechanical/acoustic measurement approach with digital signal processing (adaptive filtering, FFT analysis), the system achieves more precise measurements while reducing the complexity of physical setup and measurement infrastructure.
2Measurement precision
If multiple adaptive filters with variable step sizes are employed, then measurement precision is improved, but ease of operation deteriorates
Solution Approach 1:
The system performs self-service by automatically selecting and switching between different adaptive filter algorithms (LMS, NLMS, FIR, Wiener) based on convergence characteristics. The variable step size mechanism automatically adjusts the filtering parameters without user intervention, allowing the system to optimize measurement precision while maintaining ease of operation through automation.
Solution Approach 2:
The patent implements dynamic adaptation by allowing the step size and filter coefficients to change automatically during operation. The system dynamically adjusts the adaptive filtering parameters based on real-time convergence behavior, enabling precise measurements while keeping the user interface simple as the complexity is managed internally through dynamic parameter adjustment.
Data Source
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AI summary
This disclosure relates generally to measurement of maximum stable gain of a hearing assistance device, including but not limited to hearing aids, as a function of frequency. In various approaches an adaptive filter with a variable step size is used to determine maximum stable gain as a function of frequency. In various approaches, the determination is done in process steps performed by the hearing assistance device. In various approaches, the determination is done in process steps performed by the hearing assistance device and by a host computer.