Adaptive Microphone Directivity Control for Hearing Aids
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Solution Overview
Problem
Existing microphone systems face challenges in minimizing perceptible noise, particularly microphone noise, which increases with enhanced directivity, leading to disruptive noise artifacts and noise tails due to rapid changes in interference sources.
Innovation Solution
A method and system that utilize adaptive filtering with adjustable directivity, limiting the adaptation parameter range based on ambient noise floor comparisons to mask non-stationary microphone noise within the stationary background noise component, ensuring maximum directivity without perceptible noise artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the directivity of a directional microphone is enhanced, then interference power is reduced, but microphone noise increases
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the adaptation parameter within a limited value range based on the comparison between ambient noise floor and microphone noise figure. This allows the system to optimize directivity while preventing microphone noise from becoming perceptible, resolving the contradiction between interference reduction and noise generation.
Solution Approach 2:
The system implements dynamics by making the directivity adaptable through real-time adjustment of the adaptation parameter. The parameter range is dynamically limited based on environmental noise conditions, allowing the microphone system to achieve maximum directivity when ambient noise masks microphone noise, while reducing directivity when microphone noise would be perceptible.
2Object-affected harmful factors
If adaptive filtering is used to minimize total interference power, then overall interference is reduced, but perceptible microphone noise occurs due to delayed switching to omnidirectional operation
Solution Approach 1:
The patent applies preliminary action by proactively limiting the adaptation parameter range based on the comparison between ambient noise floor and microphone noise figure before microphone noise becomes perceptible. This prevents the delayed switching problem by establishing bounds on directivity enhancement that account for microphone noise masking conditions in advance.
Solution Approach 2:
The system implements feedback by continuously monitoring the ambient noise floor and microphone noise figure to determine the appropriate value range for the adaptation parameter. This feedback mechanism ensures that directivity is enhanced only to the extent that microphone noise remains masked by ambient noise, preventing perceptible noise artifacts.
Data Source
AI summary
A microphone system and an associated method are proposed. The microphone system comprises at least two omnidirectional, microphone signal-emitting directional microphones connected electrically to one another to establish directivity, at least one filter unit with at least one adaptation parameter for the adaptive filtering of the at least two microphone signals and a control unit to change the at least one adaptation parameter such that the sum of interference power is reduced. The value range of the at least one adaptation parameter is limited. The control unit determines limits from a comparison of the noise floor of the ambient noise with a microphone noise number. The adaptation range of an adaptive differential directional microphone is a function of stationary component of background noise, so the directivity can be selected such that the non-stationary microphone noise resulting due to directivity is masked by the stationary component of the background noise.