Hearing Device Microphone Matching via Own Voice Transfer Function
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Solution Overview
Problem
Hearing devices with separate BTE and ITE parts face challenges in maintaining optimal microphone matching after replacement or changes in the connecting element, leading to degraded beamformer performance due to mismatched microphone characteristics and altered acoustic transfer functions.
Innovation Solution
The hearing device employs a method to update the own voice transfer function by determining a complex scaling factor that minimizes the difference between the reference and updated look vectors, allowing for seamless recalibration of the microphone matching during use, even when the ITE microphone is replaced, thus maintaining effective beamforming performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of repair
If the ITE part or connecting element is replaced, then the hearing device can be repaired or upgraded, but the microphone matching and beamformer performance deteriorate due to altered acoustic transfer functions
Solution Approach 1:
The system performs preliminary characterization of the acoustic transfer function by having the user speak during a calibration phase. The impulse response is measured and stored before normal operation begins, so that when replacement occurs, the system can detect and compensate for changes by comparing against the pre-stored reference characteristics
Solution Approach 2:
The system continuously monitors the acoustic transfer function by detecting the user's voice and comparing the current impulse response against the reference stored in memory. When a replacement is detected, the system provides feedback by adjusting the beamformer weights and microphone matching parameters to compensate for the changes, thereby maintaining optimal performance
2Measurement precision
If multiple microphones are used for beamforming, then noise reduction and directional processing improve, but the complexity of matching and calibrating the microphones increases
Solution Approach 1:
The system performs self-calibration by automatically measuring the acoustic transfer function through the user's own voice. The impulse response is extracted and used to compute the appropriate matching parameters without requiring external calibration equipment or manual adjustment, thereby simplifying the process while maintaining high precision
Solution Approach 2:
The system changes the parameters of the beamformer weights and microphone matching coefficients based on the measured acoustic transfer function. By adaptively adjusting these parameters according to the actual characteristics of each microphone in the array, the system achieves optimal noise reduction and directional processing for the specific configuration
3Adaptability or versatility
If the acoustic transfer function varies due to replacement, then adaptability to new components is improved, but the beamformer performance temporarily degrades during the transition
Solution Approach 1:
The system performs preliminary measurement and storage of the acoustic transfer function characteristics before replacement occurs. This pre-characterization allows for rapid detection and compensation after replacement, minimizing the time during which performance could be degraded
Solution Approach 2:
The system dynamically adjusts the beamformer weights and microphone matching parameters in real-time based on the detected changes in acoustic transfer function. This dynamic adaptation ensures that performance is maintained continuously, with no temporary degradation during the transition from old to new components
Data Source
Figure 1A~1B
Figure 2~3
Figure 4A
AI summary
A hearing device, e.g. a hearing aid, comprises first and second separate, interconnectable parts comprising first and second input transducers, respectively, for providing first and second electric input signals, respectively, representative of sound in an environment of the user, and a beamformer filtering unit configured to provide a spatially filtered signal based thereon, and a memory comprising a previously determined own voice transfer function corresponding to a target sound source located at said user's mouth. The hearing device is configured to determine an updated own voice transfer function according to activation of a predefined trigger, when the user's own voice is present, and to store an updated own voice transfer function in said memory. The hearing device further comprises at least one combination unit configured to apply a first multiplication factor to at least one of the first and second electric input signals, and a control unit configured to determine the first multiplication factor so as to decrease, e.g. minimize a difference measure representative of a difference between the previously determined own voice transfer function and the updated own voice transfer function.