Ear Canal Model Optimization for Accurate Eardrum Sound Pressure
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Solution Overview
Problem
Existing methods for acoustically fitting hearing instruments to a user's ear fail to accurately determine the sound pressure level at the eardrum, leading to suboptimal performance due to variations in ear canal geometry.
Innovation Solution
A method involving measuring and simulating sound pressure levels in both the ear canal and a test coupler, adjusting the ear canal model's dimensions to minimize the difference between measured and simulated real-ear-to-coupler differences, thereby optimizing the acoustic fit of the hearing instrument.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If real-ear-to-coupler difference (RECD) techniques are used to create an acoustic model of the user's ear canal, then the sound pressure level at the eardrum can be determined, but the accuracy is insufficient due to variations in ear canal geometry
Solution Approach 1:
The patent applies dynamics by making the ear canal model adjustable and adaptable rather than fixed. The system dynamically adjusts model parameters (length, diameter, cross-sectional area) to match individual user measurements, allowing the acoustic model to adapt to variations in ear canal geometry. This enables accurate sound pressure level determination across diverse anatomical structures.
Solution Approach 2:
The patent utilizes parameter changes by modifying key geometric parameters of the ear canal model (length L, diameter D, cross-sectional area A) to optimize the acoustic simulation. By varying these parameters based on individual user measurements and iteratively adjusting them to minimize differences between measured and simulated sound pressure levels, the system achieves high measurement precision despite anatomical variations.
2Ease of manufacture
If the ear canal model dimensions are fixed, then the modeling process is simple, but the accuracy of sound pressure level simulation at the eardrum deteriorates
Solution Approach 1:
The patent applies preliminary action by pre-establishing a standardized ear canal model with defined geometric parameters (length L, diameter D, cross-sectional area A) that can be quickly initialized. This preliminary model serves as a starting point that is then refined through measurement comparison and optimization, combining the simplicity of a predefined model with the accuracy of customized fitting.
Solution Approach 2:
The system implements feedback by continuously comparing measured sound pressure levels (from probe tube measurements in the user's ear) with simulated sound pressure levels (from the acoustic model). The difference between measured and simulated values provides feedback that drives iterative optimization of model parameters, progressively improving simulation accuracy while maintaining a systematic and manageable process.
3Measurement precision
If probe tube measurements are taken at multiple positions in the ear canal, then the acoustic model accuracy improves, but the measurement time and complexity increase
Solution Approach 1:
The patent uses the probe tube as an intermediary measurement device that can be positioned at a specific predetermined distance from the hearing instrument sound tube end. This intermediary approach allows indirect measurement of ear canal acoustic properties without requiring complex multi-position measurements or direct eardrum contact, achieving good model accuracy with reduced measurement complexity and time.
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
This approach allows for a precise acoustic fitting of hearing instruments by iteratively optimizing the ear canal model's dimensions, ensuring accurate sound pressure level simulation at the eardrum, thereby enhancing the hearing instrument's performance across the audible frequency range.
Implementation Method 1
The sound pressure level may be determined by using real ear-to-coupler difference (RECD) techniques to create an acoustic model of the user's ear canal
Implementation Method 2
measuring the sound pressure level at a predetermined distance from the end of the sound tube of a hearing instrument positioned in the ear canal
Data Source
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AI summary
The sound pressure level at the eardrum may be determined by constructing an optimized model of the ear canal and then calculating the simulated sound pressure level at the eardrum. The model is obtained by comparing real-ear-to-coupler differences between the sound pressure level measured at a fixed distance from a hearing instrument and a simulation of the measurement, optimizing the model by varying the length and/or diameter of the canal model, repeating the simulation and determination of simulated real-ear-to-coupler difference until the differences between the measured and simulated values are minimized. The optimized real-ear-to-coupler difference at the eardrum may then be determined and in turn the sound pressure level at the eardrum may be calculated. The sound pressure level at the eardrum may then be used to acoustically fit the hearing instrument to the person.