Ear Seal Evaluation Using Dual Microphone Sound Level Differences

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing methods for evaluating the seal quality between earphones and ear canals, such as using infra-red sensors and measuring transducer impedance, require additional hardware and cannot accurately assess the seal quality, leading to issues with playback quality and ear biometrics.

Innovation Solution

A system using a first microphone outside the ear canal and a second microphone inside, with a controller to measure sound levels at test frequencies and calculate differences to determine the ear seal quality, allowing for accurate assessment without additional hardware.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Difficulty of detecting and measuring

If infra-red sensors or light sensors are used to detect ear proximity or insertion, then detection function is achieved, but additional hardware is required and seal quality cannot be assessed

Engineering Contradiction:

Improveear detection capabilityVSAvoidhardware requirements

Core Design Contradiction:

Difficulty of detecting and measuringVSDevice complexity

Solution Approach 1:

The existing microphones in the earphone device are made to serve dual functions: their original function of capturing audio and a new function of measuring ear seal quality by analyzing sound level differences at test frequencies. This eliminates the need for separate detection hardware while maintaining seal assessment capability

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The earphone's own microphones and acoustic system are utilized to perform the seal quality assessment, making the device self-diagnostic. The microphones measure both external and internal sound levels, and the processor analyzes these measurements to determine seal quality without requiring external testing equipment

Inventive Principle:

Principle #25Self-service

2Difficulty of detecting and measuring

If transducer impedance is measured to detect ear in/out status, then detection is achieved, but seal quality assessment is not possible

Engineering Contradiction:

Improveear status detectionVSAvoidseal quality assessment

Core Design Contradiction:

Difficulty of detecting and measuringVSMeasurement precision

Solution Approach 1:

The electrical measurement method (impedance measurement) is replaced with an acoustic measurement method. Instead of measuring electrical properties of the transducer, the system uses microphones to measure acoustic sound levels inside and outside the ear canal, providing more precise seal quality assessment

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The measurement parameter is changed from electrical impedance to acoustic sound level. By measuring sound pressure levels at specific test frequencies and comparing the difference between external and internal measurements, the system achieves accurate seal quality assessment that impedance measurement cannot provide

Inventive Principle:

Principle #35Parameter changes

3Measurement precision

If very low frequency probe sounds are used to measure seal quality, then seal assessment is possible, but high noise levels and microphone response inaccuracies occur

Engineering Contradiction:

Improveseal quality measurementVSAvoidnoise levels and measurement inaccuracies

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The test frequency parameter is changed from very low frequency (5 Hz) to audible test frequencies (e.g., 100 Hz, 200 Hz, 500 Hz, 1000 Hz). This change eliminates the noise and inaccuracy problems associated with ultra-low frequency measurements while still enabling seal quality assessment through sound level difference analysis

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The system plays test sounds through the earphone's speaker and uses the microphones to capture the resulting sound levels. This active feedback approach allows the system to control the test stimulus and accurately measure the seal's effect on sound transmission, avoiding the passive measurement problems of ultra-low frequency probe sounds

Inventive Principle:

Principle #23Feedback

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

Enables precise measurement of ear seal quality, improving playback and ear biometrics by determining the seal quality based on sound level differences, which can be used to enhance listening experience and assist ANC algorithms.

Implementation Method 1

The controller is configured to measure a sound level at one or more test frequencies using the first microphone, measure a sound level at the one or more frequencies using the second microphone

Methodology Applied

Scientific EffectSound level measurement: Sound

Data Source

PatentUS11516604B2System and method for evaluating an ear seal using external stimulus

Publication Date: 2022.11.29 CIRRUS LOGIC INC

AI summary

A system for evaluating a seal between an earphone of a hearing device and an ear canal that includes a first microphone positioned outside the ear canal, a second microphone positioned inside the ear canal, and a controller. The controller is configured to measure a sound level at one or more test frequencies using the first microphone, measure a sound level at the one or more frequencies using the second microphone, calculate a difference between the sound levels measured using the first and second microphones at each of the one or more test frequencies, and determine a measurement of an ear seal based on the calculated one or more differences.