Head and Torso Simulator | Binaural Measurement for Hearing Aid and Headphone Testing

A head and torso simulator (HATS) is a precision acoustic measurement instrument that replicates the acoustic scattering, diffraction, and ear canal properties of a human head, torso, and ear. Binaural microphones in the ear canal simulators measure the sound pressure at a point equivalent to the human eardrum, including all the acoustic effects of the head and body that influence how a person actually hears sounds from different directions. This makes HATS the correct measurement instrument for hearing aid testing, headphone characterisation, earphone frequency response measurement, and telecommunications audio quality assessment.

The acoustic accuracy of a HATS depends on the precision of the head and torso geometry (which determines diffraction effects and localisation cues), the accuracy of the ear canal simulator (which determines the acoustic load presented to the hearing aid or headphone), and the calibration of the embedded measurement microphones. PLACID HATS incorporates ITU-T P.57 Type 3.3 geometry, IEC 60318-4 ear canal simulators, and Class 1 pressure-field measurement microphones with ISO/IEC 17025 accredited calibration.

Key Applications

• Hearing aid testing — gain measurement to IEC 60118-8; real-ear measurements at eardrum equivalent position
• Headphone characterisation — frequency response measurement to IEC 60268-7 at the ear canal reference point
• Earphone and in-ear monitor testing — insertion gain and frequency response with IEC 60318-4 ear canal loading
• Binaural recording — spatially accurate stereo recording for psychoacoustic research and 3D audio content
• Telecommunications audio quality — headset testing and quality evaluation per ITU-T and TIA standards

Standards Compliance

• ITU-T P.57 Type 3.3: head and torso geometry specification
• IEC 60318-4: ear canal simulator for supra-aural, circumaural, and insert earphones
• IEC 60318-7: free-field ear canal equivalent reference point
• ISO 11904-1 and -2: determination of sound immission from sound sources placed close to the ear
• IEC 60118-8: hearing aids — measurement of performance of hearing aids under simulated in situ working conditions

The PLACID HATS is supplied with ISO/IEC 17025 accredited calibration for both ear canal measurement microphones, with the calibration performed with the microphones installed in the ear canal simulators to capture the complete system response. Contact PLACID for a detailed specification and quotation.

Calibration Interval and Long-Term Stability

HATS ear canal microphones should be recalibrated annually or whenever the microphone has been removed and reinstalled in the ear canal simulator. The installed sensitivity can differ from the free-field sensitivity of the microphone because the ear canal geometry changes the acoustic load. The ISO/IEC 17025 calibration certificate for the PLACID HATS states the installed sensitivity at both ear positions across the full frequency range specified by IEC 60318-4. This certificate is the primary calibration document for the complete HATS system and should be retained throughout the instrument's service life as part of the quality management calibration record.