IEC 60318-6:2007

• Abstract:

  Describes a mechanical coupler for the measurement of the output force of bone vibrators. The mechanical impedance of the coupler is specified in the frequency range 125 Hz to 8 000 Hz. The coupler is intended for calibration of audiometers using bone vibrators having a plane circular tip area of 175 mm² ± 25 mm² and for determining the performance of bone conduction hearing aids. The vibratory force developed by a bone vibrator is not, in general, the same on the coupler as on a person's mastoid. However, the IEC recommends its use as a means for the calibration of specified vibrators used in audiometry and for the exchange of specifications and of data on bone conduction hearing aids. This standard cancels and replaces IEC 60373 published in 1990. This first edition constitutes a technical revision.

• Status: Published
• Publication Date: 26-Nov-2007
• ICS: 17.140.50 - Electroacoustics
• Technical Committee: TC 29 - Electroacoustics
• Drafting Committee: WG 21 - TC 29/WG 21
• Current Stage: PPUB - Publication issued
• Start Date: 27-Nov-2007
• Completion Date: 31-Mar-2008

• Referred By: EN ISO 389-3:2016 - Acoustics - Reference zero for the calibration of audiometric equipment - Part 3: Reference equivalent threshold vibratory force levels for pure tones and bone vibrators (ISO 389-3:2016)
• Effective Date: 25-Aug-2026
• Referred By: EN ISO 389-9:2009 - Acoustics - Reference zero for the calibration of audiometric equipment - Part 9: Preferred test conditions for the determination of reference hearing threshold levels (ISO 389-9:2009)
• Effective Date: 25-Aug-2026
• Referred By: EN ISO 389-6:2007 - Acoustics - Reference zero for the calibration of audiometric equipment - Part 6: Reference threshold of hearing for test signals of short duration (ISO 389-6:2007)
• Effective Date: 25-Aug-2026

Overview

IEC 60318-6:2007 is an international standard published by the International Electrotechnical Commission (IEC) that specifies a mechanical coupler for the measurement of bone vibrators. This standard is part of the IEC 60318 series focused on electroacoustics and simulators of the human head and ear. It specifically addresses the mechanical coupler used for calibrating bone conduction audiometric equipment.

The coupler is designed to provide a standardized mechanical impedance over the frequency range of 125 Hz to 8,000 Hz, allowing the accurate measurement of output force from bone vibrators. These vibrators transmit sound through bone conduction mechanisms, typically used in audiometers and bone conduction hearing aids. IEC 60318-6 ensures consistent calibration methodology, enabling reliable performance testing and specification exchange.

This edition cancels and replaces IEC 60373 (1990), constituting a technical revision to improve measurement precision and uniformity in audiological applications.

Key Topics

• Mechanical Coupler Design
  The mechanical coupler consists of a rigid mass (~3.5 kg) that houses a force-sensing transducer topped with visco-elastic material. It presents a defined mechanical impedance when subjected to vibration, mimicking the mechanical load of the human mastoid.

• Mechanical Impedance Specifications
  Mechanical impedance is characterized by its level and phase angle within the specified frequency band. The standard defines exact impedance levels and tolerances at key audiometric frequencies (e.g., 125 Hz, 1000 Hz, up to 8000 Hz), ensuring the coupler provides a consistent load to the bone vibrator during calibration.

• Calibration Procedures
  IEC 60318-6 outlines calibration steps including the application of a static force (~5.4 N) to the coupler, environmental conditions (e.g., 23 °C temperature), and measurement uncertainty limitations to ensure accurate and reproducible results.

• Force Sensitivity and Measurement
  The force sensitivity of the mechanical coupler-that is, its response voltage relative to the applied mechanical force-is a key measurement parameter included in the standard. This ensures the output force from bone vibrators can be quantified precisely.

• Usage Notes & Limitations
  The standard notes that the vibratory force on the coupler does not exactly replicate the force on a human mastoid due to anatomical differences; however, the coupler provides a practical, reproducible reference for calibration and comparisons across devices.

Applications

• Audiometer Calibration
  The standard coupler is essential for calibrating audiometers that incorporate bone vibrators, facilitating consistent auditory threshold measurements across clinics and regions.

• Bone Conduction Hearing Aid Testing
  Manufacturers and test labs use the standardized coupler to evaluate and specify the output force characteristics of bone conduction hearing aids, improving quality control and product performance.

• Research and Development
  Researchers working on bone conduction transducers utilize the coupler for precise measurement of vibratory output, enabling innovation in hearing technologies and electroacoustic devices.

• Inter-laboratory Comparisons
  By using a common mechanical coupler standard, different laboratories achieve comparable measurement results, promoting international harmonization and regulatory compliance.

Related Standards

• IEC 60318 Series
  This part 6 standard belongs to the broader series IEC 60318, relating to simulators of the human head and ear for electroacoustic measurements.

• ISO 266 - Preferred Frequencies for Acoustics
  The standard references frequencies used in audiometry consistent with the ISO 266 preferred series for acoustical measurements.

• GUM - Guide to the Expression of Uncertainty in Measurement (BIPM, IEC, ISO, et al.)
  The calibration methodology aligns with principles described in the Guide to the Expression of Uncertainty in Measurement to quantify measurement confidence.

• IEC 60373 (1990)
  This superseded standard on bone vibrator measurement methods was replaced by IEC 60318-6 to provide an updated technical framework.

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Adopting IEC 60318-6:2007 enhances the accuracy, reliability, and standardization of bone vibrator calibration practices, benefiting audiological diagnostics and hearing aid development worldwide. Its well-defined mechanical impedance characteristics and calibration procedures ensure that professionals can achieve consistent, repeatable measurements for bone conduction hearing devices.