IEC 60126:1973

Describes a coupler for loading the earphone with a specified acoustic impedance when determining the physical performance characteristics, in the frequency range 200 Hz to 5 000 Hz, of air-conduction hearing aids using earphones coupled to the ear by means of ear inserts, e.g. ear moulds or similar devices. The use of this coupler does not allow the actual performance of a hearing aid on a person to be obtained. Its use is recommended as a simple and ready means for the exchange of specifications and of physical data on hearing aids.