Vibration Transfer Function Measurement for Bone Conduction Echo Control

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Solution Overview

Problem

Hearing devices, particularly bone conduction hearing aids, experience echo or howlround due to sound emitted by the speaker affecting the microphone through both air and vibration conduction paths, necessitating a method to efficiently evaluate and minimize the vibration transfer function.

Innovation Solution

A system and method using detectors to receive sounds at different positions, determining feedback path transfer functions through air and vibration conduction, and processing these signals to isolate the vibration transfer function using processors and databases, facilitating efficient suppression of echo.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If traditional methods are used to measure vibration transfer function, then measurement accuracy can be maintained, but device complexity and measurement difficulty increase significantly

Engineering Contradiction:
Improvevibration transfer function measurement accuracyVSAvoidmeasurement system complexity
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The patent extracts the vibration transfer function measurement from the complex traditional measurement system by using the existing microphone to detect vibration sounds. Instead of using external vibration sensors, the method isolates and measures only the vibration component through signal processing, removing the need for additional measurement devices while maintaining measurement accuracy.

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

The patent replaces the mechanical vibration measurement system with an acoustic measurement system. By using the microphone to capture vibration-induced sounds and then processing these acoustic signals to extract vibration transfer function information, the method substitutes mechanical sensors with acoustic sensors, simplifying the overall measurement system.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

2Power

If speakers emit sound in bone conduction hearing devices, then audio output is achieved, but echo and howlround occur due to feedback to microphones

Engineering Contradiction:
Improvespeaker output powerVSAvoidecho and howlround
Core Design Contradiction:
PowerVSObject-generated harmful factors

Solution Approach 1:

The patent uses feedback by measuring the vibration transfer function to enable the system to compensate for the harmful feedback path. By characterizing the vibration transmission from speaker to microphone, the system can implement active feedback cancellation to reduce echo and howlround, allowing the speaker to operate at higher power levels without excessive feedback.

Inventive Principle:
Principle #23Feedback

Solution Approach 2:

The patent converts the harmful vibration feedback into useful information by measuring the vibration transfer function. The measured vibration characteristics are then used to design compensation strategies that transform the harmful feedback path into a controllable parameter, enabling better overall system performance and echo suppression.

Inventive Principle:
Principle #22Blessing in disguise (Convert harm into benefit)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

Effectively determines and suppresses the vibration transfer function, reducing echo and improving the performance of bone conduction hearing devices by minimizing speaker interference on microphones.

Implementation Method 1

the sound produced by a bone conduction speaker will affect a microphone through vibration conduction and air conduction at the same time

Methodology Applied
Scientific EffectVibration conduction: Vibration

Implementation Method 2

feedback paths from the bone conduction speaker to the microphone include both air conduction transfer path and vibration transfer path

Methodology Applied
Scientific EffectAir conduction: Sound

Data Source

PatentEP4120690B1Method and system for obtaining vibration transfer function
Publication Date: 2025.09.10 SHOKZ HEARING PTE LTD
  • EP4120690B1 patent drawingFigure 1
  • EP4120690B1 patent drawingFigure 2
  • EP4120690B1 patent drawingFigure 3

AI summary

The present disclosure provides a method for obtaining a vibration transfer function from a sound generation unit to other positions. The method comprises: generating a first sound and a second sound based on a first test audio signal and a second test audio signal; outputting a first feedback signal after receiving the first sound, the first feedback signal including a signal transmitted from a sound generation unit to a first position through vibration transmission path and air conduction transmission path; outputting a second feedback signal after receiving the second sound, the second feedback signal including a signal transmitted from the sound generation unit to a second position through air conduction transmission path; determining the vibration transfer function from the sound generation unit to the first position based on the first test audio signal, the second test audio signal, the first feedback signal, and the second feedback signal.