Earphone Coupler With Adjustable Leakage for ANC Measurement
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Solution Overview
Problem
Existing ear-canal simulators, such as the IEC 60318-4 (711-type coupler), are not well suited for accurately measuring earphones with active noise cancellation (ANC) due to inconsistent acoustic leakage and mismatched acoustic transfer functions when loose-fitting or acoustic leakage occurs.
Innovation Solution
A redesigned coupler with adjustable leakage paths and acoustic resonators simulating the ear canal, allowing for adjustable acoustic resistance and better matching the acoustic response of a real ear, including Helmholtz resonators and adjustable vents to simulate various leakage conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a standardised 711-type coupler is used to measure earphone characteristics, then the sealed acoustic impedance matching is achieved in the frequency range of 100 Hz to 10 kHz, but the measurement accuracy deteriorates when acoustic leakage occurs due to inconsistent acoustic transfer function from speaker to microphone
Solution Approach 1:
The coupler incorporates adjustable leakage paths that can be dynamically modified to simulate different leakage conditions. The leakage path includes a variable aperture mechanism that allows the acoustic resistance to be changed, enabling the coupler to adapt from completely sealed conditions to various degrees of acoustic leakage, thus maintaining measurement accuracy across different fitting scenarios
Solution Approach 2:
The acoustic resistance of the leakage path is made variable by introducing an adjustable aperture or mesh structure. This allows the acoustic parameters of the coupler to be changed to match different real-ear leakage conditions, improving the accuracy of ANC filter design measurements by selecting appropriate resistance values corresponding to different earphone fit qualities
2Measurement precision
If the leakage path aperture is reduced to increase acoustic resistance and better simulate real-ear leakage, then the acoustic transfer function matching improves, but the device complexity increases due to additional adjustment mechanisms
Solution Approach 1:
The complexity is localized to the leakage path region where an adjustable aperture or mesh is introduced, while the rest of the coupler structure remains simple and standardized. This allows the acoustic transfer function matching to be improved through localized parameter adjustment without requiring complete redesign of the entire coupler system
Solution Approach 2:
A simple adjustable mechanism such as a movable plug, rotating aperture, or interchangeable mesh screens is introduced into the leakage path. This dynamic element allows the acoustic resistance to be modified to match different leakage conditions while maintaining overall structural simplicity through minimal moving parts or interchangeable components
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
The redesigned coupler extends the frequency range of matching to the real-ear, providing a better match of sealed acoustic impedance and simulating realistic leakage conditions, enhancing ANC design processes.
Implementation Method 1
The one or more acoustic resonators may each comprise a chamber (having a resonator volume) and a neck portion connecting the chamber to the main channel. The neck portion may comprise an acoustic resistive element for changing the acoustic resistance of the neck portion.
Implementation Method 2
The acoustic resonator(s) may comprise a first acoustic resonator configured to have a fundamental resonance frequency in the range of 500 Hz to 1 KHz. A second acoustic resonator may be configured to have a fundamental resonance frequency in the range of 3.85 kHz to 5 KHz.
Implementation Method 3
The neck portion may comprise an acoustic resistive element for changing the acoustic resistance of the neck portion. The acoustic resistive element may comprise an obstruction with a slit or other aperture or preferably an acoustic mesh provided across the neck portion to increase the acoustic resistance of the neck portion.
Data Source
AI summary
A coupler for an acoustic device includes a main opening for inserting the acoustic device or an adapter for the acoustic device. The coupler also includes a main channel connected at one end to the main opening. The coupler further includes one or more leakage paths for allowing sound to escape the main channel when in use. The coupler additionally includes one or more acoustic resonators connected to the main channel. The one or more acoustic resonators includes a first acoustic resonator configured to have a fundamental resonance frequency in the range of 500 Hz to 1 kHz and a second acoustic resonator configured to have a fundamental resonance frequency in the range of 3.85 kHz to 5 kHz.