IEC 60318-3:2014 specifies an acoustic coupler for the measurement of supra-aural audiometric earphones in the frequency range from 125 Hz to 8 000 Hz. The sound pressure developed by an earphone is not, in general, the same in the coupler as in a person's ear. However, the acoustic coupler can be used as an objective and reproducible means of measuring the output of supra-aural earphones. It can be used for specifying reference equivalent threshold sound pressure levels for the calibration of audiometers. This second edition cancels and replaces the first edition published in 1998 and constitutes a technical revision which includes the following significant technical changes with respect to the previous edition:- adjustment of terms and wording to the other parts of IEC 60318;- introduction of maximum permitted uncertainties;- and revised requirements for static pressure equalization.Keywords: electroacoustics, deafness, hearing aids