Overview
IEC 60318-8:2022 is an international standard developed by the International Electrotechnical Commission (IEC) that specifies the requirements for an acoustic coupler used in high-frequency measurements of hearing aids and earphones coupled to the ear by means of ear inserts. This standard is part of the IEC 60318 series, which focuses on electroacoustics simulators of the human head and ear.
The acoustic coupler defined in IEC 60318-8 provides a specified acoustic impedance load to air-conduction hearing aids and earphones up to a frequency of 16 kHz. Although it does not simulate the human ear directly, its small effective volume of 0.4 cm³ minimizes resonances, thereby enabling repeatable and reliable acoustic performance testing with low measurement uncertainty.
Key Topics
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Acoustic Coupler Design
The standard outlines precise mechanical design specifications, including cavity dimensions and an effective volume of 0.4 cm³. This small volume ensures minimal resonance effects below 16 kHz, making it suitable for high-frequency audiometry applications.
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Acoustic Impedance Specification
IEC 60318-8 defines the acoustic transfer impedance level modulus along with acceptance intervals to ensure consistent coupler performance, facilitating accurate testing environments.
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Coupling Methods
Various coupling techniques are covered for connecting hearing aid receivers and earphones to the coupler, including:
- Coupling via tubing to hearing aid receivers
- Connection to in-the-ear (ITE), in-the-canal (ITC), and completely-in-the-canal (CIC) hearing aids
- Receiver-in-canal (RIC) coupling
- Behind-the-ear (BTE) hearing aids with continuous diameter tubing or earmould simulators
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Calibration and Verification
The standard includes methods for calibration under specified environmental conditions to ensure measurement accuracy. Additionally, there are procedures for verifying effective volume and acoustic transfer impedance.
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Measurement Uncertainty and Conformance
IEC 60318-8 specifies maximum permissible expanded uncertainty levels for conformance testing, with example assessments and test setups provided in the annexes.
Applications
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High-Frequency Audiometry Testing
The coupler supports extended high-frequency audiometry by providing reliable acoustic impedance loading, enabling precise performance measurements of hearing aids and earphones designed for frequencies up to 16 kHz.
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Hearing Aid and Earphone Quality Assurance
Manufacturers and testing laboratories can utilize the acoustic coupler defined in IEC 60318-8 to perform repeatable, low-uncertainty acoustic tests during product development and final quality control.
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Standardized Acoustic Measurement
Using this standardized coupler ensures consistency across international testing procedures, facilitating compliance with regulatory requirements and harmonizing measurement results globally.
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Research and Development
The detailed mechanical and acoustic specifications assist researchers in developing and refining hearing aid and earphone technologies optimized for accurate high-frequency sound reproduction.
Related Standards
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IEC 60318 Series
Other parts of the IEC 60318 series address simulators of the human head and ear for various electroacoustic measurements, offering complementary methodologies for hearing device evaluation.
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IEC 60118 Series
Standards focusing on electroacoustics performance testing for hearing aids, covering aspects such as measurement methodology and performance criteria.
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ITU-T P.58 and ITU-T P.59
International Telecommunication Union standards related to headphone and earphone measurements that complement IEC guidelines.
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ISO 389 Series
International standards providing reference thresholds and methods for audiometric testing setups, relevant for high-frequency hearing assessments.
Keywords: IEC 60318-8, acoustic coupler, hearing aid testing, earphones, ear inserts, high-frequency audiometry, acoustic impedance, electroacoustics, standardization, hearing device measurement, IEC standards
Open preview (PDF)Electroacoustics - Simulators of human head and ear - Part 8: Acoustic coupler for high-frequency measurements of hearing aids and earphones coupled to the ear by means of ear inserts
