Insert earphones--a comparison of short-duration signals measured with an occluded ear simulator and a 2cc coupler

The responses of several insert earphones in the Etymotic 3A series were measured with the occluded ear simulator (IEC 60711) and the 2cc coupler (IEC 60126). Acoustic clicks following a 100 us rectangular voltage pulse were compared. The peak-to-peak equivalent sound pressure levels in the ear simulator were found to be 9.2 dB greater than those in the 2cc coupler. The difference was independent of type of earphone among those tested. Similar comparisons were made for tone pips (brief tones or tone bursts) and continuous tones. For a given drive voltage, differences in earphone output were almost the same as the corresponding differences in published RETSPLs for the occluded ear simulator and 2cc coupler (ISO 389-2).