DIFFERENCE LIMEN AND RECRUITMENT

Abstract

THE NEED for the measurement of recruitment is apparent in the speed with which "recruitment tests" have been provided by manufacturers of audiometers and are incorporated in clinical routines, even before sufficient validating work has been done. This need presumably arises in connection with diagnosis. No one doubts by now that the presence of recruitment is indicative of a nonconductive hearing loss. Furthermore, if the thesis of Dix, Hallpike, and Hood¹ is substantiated, even finer diagnoses can distinguish between cochlear and retrocochlear pathologies. Recruitment is defined primarily as a more-rapid-than-normal increase in subjective loudness for a given increase in physical intensity. It is most readily explored, according to this definition, by the binaural loudness balance, described originally by Fowler.² In this technique one measures the intensities of two tones (one presented to the left, the other to the right ear) when the listener reports that they sound equally