Acoustics. Reference zero for the calibration of audiometric equipment - Reference equivalent threshold force levels for pure tones and bone vibrators

Acoustics. Reference zero for the calibration of audiometric equipment - Reference equivalent threshold force levels for pure tones and bone vibrators

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1   Scope

This part of ISO 389 specifies the following data applicable to the calibration of bone vibrators for pure-tone bone-conduction audiometry.
  1. a) Reference equivalent threshold force levels (RETFLs), corresponding to the threshold of hearing of young otologically normal persons by bone-conduction audiometry. RETFL is the vibratory force level transmitted to a mechanical coupler of specified characteristics (see 5.3) by a vibrator when applied to the mechanical coupler under stated conditions of test and when energized at the voltage level corresponding to the normal threshold of hearing for location on the mastoid prominence.

    NOTE 1 Interim values for the differences in reference equivalent threshold force levels between location on the forehead and mastoid are included for information in annex C.

  2. b) Essential characteristics of the bone vibrator and of its method of coupling to a person under test and to the mechanical coupler.
  3. c) Essential characteristics and datum level of the masking noise applied to the ear not under test.
    Guidance on the practical application of this part of ISO 389 in the calibration of audiometers is given in annex B.

    NOTE 2 Recommended procedures for carrying out bone-conduction audiometry are specified in ISO 8253-1.