Hearing Aid Feedback Transition Threshold Algorithm

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Hearing aids face challenges in effectively reducing acoustic feedback, particularly when the external feedback path rapidly changes, leading to unstable feedback loops and audible artifacts, as existing algorithms struggle to accurately identify and correct feedback in dynamic conditions.

Innovation Solution

A feedback transition threshold algorithm that assesses short duration trouble indicators, such as correlation coefficients, to quickly reduce gain in frequency bands experiencing rapid feedback changes, and smoothly returns to full gain once stability is achieved, using a correlation detector and adaptive FIR filter to minimize feedback squeal.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If feedback cancellation processing algorithms are used to reduce acoustic feedback, then feedback squeal is reduced and more gain can be achieved, but the algorithms struggle to accurately identify and correct feedback when the external feedback path rapidly changes

Engineering Contradiction:

Improvefeedback cancellation accuracyVSAvoidresponse to rapid feedback path changes

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent implements dynamic gain adjustment where the processing algorithm adapts its behavior based on detected feedback conditions. When rapid feedback path changes are detected through correlation analysis, the system dynamically modifies the feedback cancellation approach by reducing gain in affected frequency bands, allowing the system to respond adaptively to changing acoustic conditions rather than using a static processing approach

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes processing parameters (gain values, frequency band selections) based on real-time analysis of feedback characteristics. By monitoring correlation coefficients and identifying when the feedback path changes rapidly, the algorithm adjusts its parameters to maintain effective feedback cancellation under varying acoustic conditions, transitioning between different processing states as needed

Inventive Principle:

Principle #35Parameter changes

2Object-affected harmful factors

If gain is reduced in frequency bands experiencing rapid feedback changes, then feedback squeal is minimized, but sound quality may be degraded

Engineering Contradiction:

Improvefeedback squeal reductionVSAvoidsound quality

Core Design Contradiction:

Object-affected harmful factorsVSLoss of information

Solution Approach 1:

The patent applies gain reduction locally only to specific frequency bands where rapid feedback path changes are detected, rather than reducing gain across all frequencies. The correlation detector identifies problem frequency bands, and the feedback cancellation algorithm applies targeted gain adjustment only to those specific bands, preserving sound quality in frequency ranges that do not exhibit feedback instability

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The system applies partial gain reduction only when and where feedback issues are detected, rather than continuously reducing gain across all bands. By using correlation analysis to identify specific moments and frequency bands requiring intervention, the algorithm applies just enough gain reduction to suppress feedback squeal while minimizing impact on overall sound quality

Inventive Principle:

Principle #16Partial or excessive action

3Object-affected harmful factors

If the hearing aid is fitted tightly into the ear canal to minimize acoustic feedback transmission, then feedback is reduced, but comfort is compromised and occlusion effect occurs

Engineering Contradiction:

Improveacoustic feedback transmissionVSAvoidcomfort and natural voice perception

Core Design Contradiction:

Object-affected harmful factorsVSEase of operation

Solution Approach 1:

The patent replaces the mechanical solution of tight physical fitting with an electronic processing solution. Instead of relying on a tight seal in the ear canal to prevent acoustic feedback, the system uses correlation-based detection and digital signal processing to identify and cancel feedback paths, allowing the hearing aid to be fitted more comfortably without compromising feedback reduction effectiveness

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The feedback cancellation algorithm acts as an intermediary between the microphone input and amplifier output, processing the electrical signal to remove feedback components. This electronic intermediary approach to feedback reduction eliminates the need for tight mechanical fitting, as the feedback is addressed through signal processing rather than physical isolation

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS8355517B1Hearing aid circuit with feedback transition adjustment

Publication Date: 2013.01.15 INHEARING TECHNOLOGY INC

AI summary

A feedback transition threshold algorithm assesses and responds to feedback transition events in a hearing aid. The feedback transition threshold algorithm considers short duration trouble indicators, with the preferred primary short duration trouble indicators being the correlation witnessed between the incoming signal in a given frequency band and the same signal delayed by the estimated feedback loop time. If the short duration trouble indicators indicate that feedback squeal is likely and that the external feedback path is changing too quickly for accurate correction by the internal adaptive feedback reduction filter, when the signal level crosses the feedback transition threshold gain is reduced in that frequency band.