scope:

This standard specifies requirements for mechanical couplers used for calibrating bone-conduction audiometers and for making measurements on bone vibrators and bone-conduction hearing aids, in the frequency range from 125 to 8000 hertz (Hz) inclusive.

Audiometry

The purpose of this standard, as applied to audiometry, is to provide a means of calibrating bone vibrators of the types used in bone-conduction audiometry by specifying a standardized mechanical impedance with which to load the vibrator and a device for measuring the alternating force produced. Reference equivalent threshold force levels corresponding to the normal threshold of hearing are specified by American National Standard Reference Equivalent Threshold Force Levels for Audiometer Bone Vibrators, S3.26-1981, or future revisions thereof. For this application, the bone vibrator is required to have a plane circular tip area of 175 ± 25 mm² and to be applied to the mechanical coupler with a static force of 5.4 ± 0.5 newton (N). The mechanical coupler is also intended for other measurements on bone vibrators for audiometers, viz., frequency response, unwanted sound radiation, harmonic distortion, etc.

Hearing Aids

The purpose of this standard, as applied to hearing aids, is to provide a means of measuring the electromechanical characteristics (sensitivity, frequency response, harmonic distortion, etc.) of bone vibrators used in hearing aids, or the acoustomechanical characteristics of complete hearing aids of the bone conduction type, when dynamically loaded by a specified mechanical impedance and statically loaded with a force in the range 1.7 to 4 N.