This standard gives recommendations for the measurement of the performance characteristics of airconduction hearing aids based on a free-field technique and measured with an acoustic coupler. Described are the recommended methods of measurement for the evaluation of the electroacoustical characteristics of hearing aids e.g. for type testing and manufacturer data sheets. The methods are chosen to be practical and reproducible, consequently based on fixed parameters chosen, to a certain extent arbitrarily. This should be taken into consideration when comparisons are being made between test results for hearing aids of different models and manufacture. The test results obtained by the methods of this standard will express the performance under conditions of the test and may deviate substantially from the performance of the hearing aid under practical conditions for use. This standard will use an acoustic coupler according to IEC 60318-5 which is only intended for loading a hearing aid with a specified acoustic impedance and is not intended to model the sound pressure in a person’s ear. It should be noted that the use of this acoustic coupler will yield different results from using the occluded ear simulator of IEC 60318-4 as used in former versions of this standard. For the measurement of the performance characteristics of hearing aids for simulated in situ working conditions, IEC 60118-8 can be used. For measurement of hearing aids under typical user settings and using a speech like signal, IEC 60118-15 can be used. Though the number of measurements covered by this standard is limited, it is not intended that all measurements described herein shall be made in every case. In cases of custom-made in-the-ear instruments, the data supplied by the manufacturer applies only to the particular hearing aid being tested. For the measurement of the performance characteristics of hearing aids for production, supply and delivery quality assurance purposes, IEC 60118-7 can be used. Compared to IEC 60118-7, this standard requires more precise measurement equipment and the frequency range has been extended to 8 kHz versus 5 kHz in IEC 60118-7.
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