IEC 60318-4:2010 describes an occluded-ear simulator intended for the measurement of insert earphones in the frequency range from 100 Hz to 10 000 Hz. It is suitable for air conduction hearing aids and earphones, coupled to the ear by means of ear inserts e.g. ear moulds or similar devices. The occluded-ear simulator is also suitable as the basis for an extension intended to simulate the complete ear canal and the outer ear (for instance in head simulators). The occluded-ear simulator simulates the acoustic transfer impedance for the occluded normal adult human ear. However, it does not simulate the leakage between an earmould and a human ear canal; therefore, the results obtained with the occluded-ear simulator may deviate from the performance of an insert earphone on a real ear, especially at low frequencies. Moreover, large performance variations among individual ears will occur which should be considered when using the ear simulator. Above 10 kHz the device does not simulate a human ear, but can be used as an acoustic coupler at additional frequencies up to 16 kHz. Below 100 Hz, the device has not been verified to simulate a human ear, but can be used as an acoustic coupler at additional frequencies down to 20 Hz. IEC 60318-4:2010 cancels and replaces IEC 60711, published in 1981 and constitutes a technical revision. The main changes with respect to the previous edition are listed below:
- extension of the usable frequency range to 100 Hz - 16 000 Hz;
- addition of values of maximum permitted expanded uncertainties to all tolerances.