equivalent threshold level (monaural earphone listening)

4.29  equivalent threshold level (monaural earphone listening). At a specified frequency, for a specified type of earphone, and for a stated force of application of the earphone to a human ear, the sound pressure level set up by the earphone in a specified coupler or artificial ear when the earphone is activated by that voltage which, with the earphone applied to the ear concerned, would correspond with the threshold of hearing. Abbreviation, ETSPL; unit, decibel (dB).