4.30  equivalent threshold force level (monaural listening). At a specified frequency, for a specified configuration of a bone vibrator on a specified mechanical coupler, the vibration force level set up by the bone vibrator in a specified coupler when the bone vibrator is activated by that voltage which, with the bone vibrator applied to the mastoid concerned, would correspond with the threshold of hearing. Abbreviation, ETFL; unit, decibel (dB).

Annotation         The non-test ear must be masked.

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