Long Term Feedback Path Estimate in Hearing Aids
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Solution Overview
Problem
Existing listening devices, particularly hearing aids, face challenges in providing a reliable long-term estimate of the feedback path due to changes in ear canal conditions, such as those caused by children's rapid ear growth, leading to acoustic feedback issues like howling, which current technologies struggle to accurately detect and mitigate.
Innovation Solution
A method and device that utilize a feedback estimation unit to provide a reliable long-term feedback path estimate by analyzing detectors' signals for acoustic environment properties, filtering out unreliable estimates, and adjusting gain settings to prevent feedback instability, incorporating a slow online feedback manager to account for slow changes in ear mold fit and ear canal growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a fast online feedback manager is used to estimate current feedback path, then the response speed to feedback changes is improved, but the reliability of long term feedback estimate deteriorates due to short term acoustic variations
Solution Approach 1:
The patent divides the feedback estimation into two separate components: a fast online feedback manager for rapid response to feedback changes, and a slow online feedback manager for reliable long-term estimation. Each component operates independently with its own filtering characteristics, allowing the system to benefit from both speed and reliability without one compromising the other.
Solution Approach 2:
The patent introduces a criterion evaluation mechanism that acts as an intermediary between the fast and slow feedback estimators. This criterion determines whether current feedback estimates should influence the long-term estimate, filtering out unreliable short-term variations while preserving genuine feedback path changes.
2Measurement precision
If current feedback path estimates are directly used for long term estimate, then the tracking of feedback changes is improved, but the accuracy deteriorates due to inclusion of unreliable estimates from short term acoustic variations
Solution Approach 1:
The patent applies preliminary filtering and criterion evaluation to current feedback estimates before they are incorporated into the long-term estimate. This preliminary action removes unreliable estimates caused by short-term acoustic variations, ensuring that only valid feedback path changes contribute to the long-term estimation.
Solution Approach 2:
The system uses feedback from the criterion evaluation to control the updating of the long-term feedback estimate. When the criterion indicates unreliable conditions (such as short-term acoustic variations), the update is suppressed or reduced, preventing degradation of the long-term estimate accuracy.
3Reliability
If gain is increased to improve audio quality, then the audio quality is improved, but acoustic feedback instability increases
Solution Approach 1:
The patent implements a feedback control mechanism where the long-term feedback path estimate is continuously monitored and used to adjust the maximum allowable gain. When the estimate indicates increased feedback path gain (which would lead to instability), the system proactively reduces the maximum gain to prevent howling, thus maintaining stability while preserving audio quality within safe limits.
Data Source
AI summary
A method provides a long term feedback path estimate of a listening device. The method comprises a) providing an estimate of the current feedback path; b) providing a number of detectors of parameters or properties of the acoustic environment of the listening device and/or of a signal of the listening device, each detector providing one or more detector signals; c) providing a criterion for deciding whether an estimate of the current feedback path is reliable based on said detector signals; d) storing said estimate of the current feedback path, if said criterion IS fulfilled and neglecting said estimate of the current feedback path, if said criterion is NOT fulfilled; e) providing a long term estimate of the feedback path based on said stored estimate(s) of the current feedback path.