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 earilier 2 cm coupler.
The use of this couple does not allow the actual performance of a hearing aid 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.
BS 6111:1981 history
2006BS EN 60318-5:2006 Electroacoustics - Simulators of human head and ear - 2 cm3 coupler for the measurement of hearing aids and earphones coupled to the ear by means of ear inserts
1981BS 6111:1981 Specification for reference coupler for the measurement of hearing aids using earphones coupled to the ear by means of ear inserts