Hearing Aid Matched Filter for Accurate Critical Gain Measurement
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Solution Overview
Problem
Existing methods for measuring the individual threshold of feedback in hearing aids are inaccurate due to background noise, which affects the signal-to-noise ratio, making it difficult to determine the critical gain for reducing unwanted whistling sounds.
Innovation Solution
The implementation of a matched filter in hearing aids to improve signal identification from noise by correlating input signals with known waveforms, enhancing the signal-to-noise ratio and allowing for more accurate critical gain measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If an acoustic test signal is fed directly into a level meter to measure critical gain, then the measurement procedure is simple, but the measurement accuracy deteriorates due to background noise affecting the signal-to-noise ratio
Solution Approach 1:
The measurement system is segmented into multiple functional components: a signal generator producing test signals, a hearing instrument under test, a measurement microphone capturing the output, and a matched filter specifically tuned to the test signal waveform. This segmentation allows the matched filter to isolate the test signal from background noise through correlation processing, thereby improving measurement accuracy while maintaining procedural simplicity
Solution Approach 2:
A matched filter is introduced as an intermediary component between the level meter and the noisy acoustic environment. This filter acts as a mediator that selectively passes the test signal frequency while attenuating background noise, enabling accurate critical gain measurement without requiring complex measurement procedures
2Object-affected harmful factors
If the output level of the acoustic test signal is limited to avoid discomfort, then the hearing instrument wearer's comfort is improved, but the signal-to-noise ratio deteriorates
Solution Approach 1:
The system changes the parameter of signal detection by using a matched filter that correlates with the known test signal waveform. This allows the use of lower amplitude test signals (reducing discomfort) while maintaining adequate signal-to-noise ratio through coherent integration in the correlation process, which provides processing gain proportional to the observation time
Data Source
AI summary
The invention relates to a hearing aid system comprising an input transducer for converting an input sound signal comprising an information signal part of a known waveform and a background noise part to an electrical analogue input signal, optionally an A/D converter for converting the electrical input signal to a digital input signal. The invention further relates to a method of making a critical gain measurement. The object of the present invention is to improve the signal-to-noise ratio of a signal to be measured or detected in a hearing instrument compared to prior art solutions. The problem is solved in that a matched filter receiving said analogue or digital input signal and optimized to improve the identification of the information signal part from the noisy input signal. An advantage of the invention is that it provides an alternative scheme for improving signal to noise ratio of a hearing aid. The invention may e.g. be used for the customization of hearing aid parameters in cooperation with fitting software and/or for improving signal to noise ratio of a detected or measured signal.