scope:

The object of this recommendation is to describe a coupler for loading the earphone with a specified acoustic impedance when determining the physical performance characteristics, in the frequency range 200 Hz to 5000 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 coupler described is a development of an earlier 2 cm3 coupler. The use of this coupler does not allow t he actual performance of a hearing acid on a person to be obtained; however the IEC recommends its use as a simple and ready means for the exchange of specifications and of physical data on hearing aids.