Hearing Aid Microphone Noise Reduction via Adaptive Wiener Filtering
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Solution Overview
Problem
Condenser microphones in hearing devices produce residual noise that can be amplified in quiet environments, making it difficult for users to distinguish ambient sounds from microphone noise, especially due to temperature and aging-related changes in noise power spectral density, which existing compression methods struggle to compensate for.
Innovation Solution
A method and apparatus that utilize a Wiener filter to attenuate microphone noise by determining noise power and deactivating the filter when noise levels exceed a predetermined limit, with a gain weighting factor and gradual transition between active and inactive states, allowing for continuous adjustment to noise spectral density changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a compressor is used to attenuate microphone noise in quiet environments, then microphone noise is reduced, but ambient sounds may be unintentionally attenuated and audio quality deteriorates
Solution Approach 1:
The patent applies a Wiener filter that dynamically adjusts its attenuation parameter based on the estimated noise power spectral density. By continuously monitoring the input signal and adapting the filter coefficients according to changing noise conditions, the system achieves effective noise suppression while preserving ambient sounds, resolving the contradiction between noise reduction and audio quality maintenance
Solution Approach 2:
The system implements a feedback mechanism where the noise power spectral density is continuously estimated from the input signal and used to adjust the Wiener filter parameters in real-time. This closed-loop control allows the system to distinguish between microphone noise and ambient sounds, attenuating only the noise component while maintaining audio fidelity, thus resolving the contradiction between noise suppression and sound quality
2Reliability
If frequency-selective amplification is applied to compensate for hearing loss, then hearing assistance is improved, but microphone noise is amplified along with the desired frequencies
Solution Approach 1:
The patent segments the frequency spectrum into multiple channels and applies independent noise suppression processing to each channel. The Wiener filter operates on individual frequency bins, allowing selective attenuation of noise components while preserving amplified hearing assistance frequencies. This channel-by-channel approach resolves the contradiction by treating noise and desired signal separately in the frequency domain
Solution Approach 2:
The system dynamically changes the attenuation parameter of the Wiener filter based on the estimated noise power spectral density in each frequency channel. By adapting the filter gain according to the local noise conditions, the system can suppress noise in amplified frequency regions without compromising the overall hearing assistance effect, thus resolving the contradiction between hearing improvement and noise reduction
3Ease of manufacture
If a fixed characteristic curve compressor is used, then implementation is simple, but temperature and aging-related noise changes cannot be compensated
Solution Approach 1:
The patent transforms the static compressor characteristic curve into a dynamic Wiener filter whose parameters adapt in real-time to changing noise conditions. The system continuously estimates the noise power spectral density and adjusts the filter coefficients accordingly, enabling compensation for temperature and aging-related noise variations. This dynamic adaptation resolves the contradiction between implementation simplicity and noise compensation capability
Solution Approach 2:
The Wiener filter implementation includes self-adjusting mechanisms where the system automatically estimates noise parameters and updates filter coefficients without external intervention. The noise power spectral density estimation and filter parameter optimization are performed autonomously by the system itself, providing adaptability to environmental changes while maintaining relatively simple implementation through standardized signal processing algorithms
Data Source
AI summary
An input signal is provided with a low microphone noise in a hearing apparatus. The microphone noise in the input signal of the hearing apparatus is reduced, by the input signal being filtered by a Wiener filter, if a noise power determined at the input signal is smaller than a predetermined limit value. The Wiener filter is however deactivated, if the noise power is greater than the limit value or equal to the limit value.