Hearing Aid Acoustic Path Compensation for Low-Frequency Noise
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Solution Overview
Problem
Hearing aids with concurrent acoustic and electrical signal paths struggle to effectively suppress noise, particularly in the low-frequency range, due to interference from the acoustic signal entering the auditory canal, which impairs noise reduction methods like directional microphones.
Innovation Solution
A hearing aid with an estimating device for usable and interfering signals, a signal-processing device to simulate the acoustic path's transfer function, and a combing device to combine these signals, allowing for quick compensation of sound interference reaching the eardrum, using either linear or time-variant transfer functions and dynamic adaptation based on acoustic sensor feedback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional noise suppression methods (directional microphones) are used, then noise reduction is achieved, but concurrent acoustic signal paths strongly impair the noise suppression in the low-frequency range
Solution Approach 1:
The signal processing is segmented into separate electrical and acoustic paths. The electrical signal processing handles high-frequency noise suppression, while the acoustic signal path handles low-frequency compensation, dividing the frequency range into distinct processing domains to avoid mutual interference
Solution Approach 2:
A transfer function acts as an intermediary to model and predict the acoustic signal path. This transfer function serves as a mediator that translates the electrical signal into its acoustic equivalent, allowing the system to compensate for acoustic path effects without directly interfering with the electrical signal processing
2Measurement precision
If the acoustic path is compensated using a complex time-variant transfer function, then accuracy is improved, but computing time increases
Solution Approach 1:
The transfer function is made dynamically adjustable between linear (time-invariant) and time-variant modes. The system can switch between these modes based on operating conditions, allowing accurate time-variant processing when needed while using computationally efficient linear processing during normal operation
Solution Approach 2:
The complexity parameter of the transfer function is changed based on requirements. The system can adjust the degree of time-variation in the transfer function, transitioning from simple linear parameters to more complex time-variant parameters only when accuracy requirements demand it
3Ease of operation
If the hearing aid is designed with open supply or venting holes, then comfort and通气性 are improved, but concurrent signal paths arise that strongly impair noise suppression
Solution Approach 1:
The acoustic signal path that was previously considered harmful (causing interference) is converted into a beneficial component. By modeling and compensating for this acoustic path, the system uses the very path causing interference to generate a compensating signal that actively reduces low-frequency noise, turning the disadvantage into an advantage
Data Source
AI summary
Concurrent signal paths going pass a hearing aid bring about interferences in the auditory canal. These interferences are compensated by estimating an interfering signal from the input signal disturbed by interference from a microphone and applying to the interfering signal a transfer function, with which the concurrent acoustic signal path is simulated, thereby forming an interfering output signal, and combining a usable output signal from a signal-processing device with the interfering output signal. In this way, a noise suppression by directional microphone switching configurations can be made possible when concurrent signal paths do not make such directional microphone switching possible by conventional approaches.