Hearing Device ANC Using Microphone Coherence Classification
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Solution Overview
Problem
Existing active noise cancellation (ANC) systems in hearing devices face limitations in effectively controlling noise, particularly due to reliance on wind noise and handling noise detection methods that do not accurately represent the ambient sound environment.
Innovation Solution
The method involves using a microphone system with two microphones, one external and one internal to the ear canal, to capture audio signals. These signals are processed to determine a coherence measure, which is used to classify the ambient sound environment. The ANC system then generates a feed-forward compensating signal based on this classification, improving noise control by mixing the audio signals with the compensating signal at a ratio dependent on the ambient sound classification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If ANC system controls based on wind noise and handling noise detection, then specific noise sources can be targeted, but the noise control effectiveness is reduced because these noise sources do not accurately represent the ambient sound environment
Solution Approach 1:
The patent extracts the ambient sound detection function from the ear canal microphone signal by using only the outer microphone signals to determine ambientness. This separation allows the ANC system to focus on environmental noise characteristics rather than being contaminated by non-ambient noise sources like wind and handling noise, thereby improving noise control effectiveness
Solution Approach 2:
The patent introduces an ambientness detection mechanism that uses coherence measurement between outer microphone signals as an intermediary to classify ambient sound environments. This intermediary layer enables the ANC system to accurately identify and control environmental noise without being affected by poor-quality noise sources
2Object-affected harmful factors
If ANC system uses feed-forward compensating signal with high mixing ratio, then noise cancellation is improved, but non-ambient noise sources such as wind noise and handling noise create interference
Solution Approach 1:
The patent dynamically adjusts the mixing ratio of the feed-forward compensating signal based on the determined ambientness classification. The mixing ratio is increased when ambient sound is detected and decreased when non-ambient noise is detected, allowing the ANC system to optimize noise cancellation performance while minimizing interference from non-environmental noise sources
Solution Approach 2:
The patent implements a feedback mechanism where the ambientness classification based on outer microphone coherence continuously informs the mixing ratio adjustment. This feedback loop enables the ANC system to adapt to changing sound environments and maintain optimal performance by reducing the influence of non-ambient noise sources
Data Source
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AI summary
A hearing device having ambient noise control.