WHEN it was reported in 1948 by Dix et al1 that loudness recruitment was typically present in cochlear sensory neural hearing loss but, typically absent in VIIIth nerve sensory neural hearing loss the clinical significance of this finding was quickly realized. It suggested that results of measurement of the loudness recruitment phenomenon could be used as a diagnostic in the differentiation of cochlear and retrocochlear loss. Therefore, a search for a simple, easily-administered clinical test for recruitment commenced and intensity difference limen (DL) received attention as a possible indirect measure of recruitment. However, although DL measurement seemed to be a straight-forward and uncomplicated process, the experimental results among several investigators have differed greatly. As a result, until recently no comprehensive statement describing this loudness domain has emerged. Through the years it has been accepted that these differences in DL size arose because of varying experimental procedures, stimulus conditions, individual
Horner JS, Dallos P. Cumulation of Just Noticeable Difference for Intensity in Normal and Impaired Ears. Arch Otolaryngol. 1969;90(3):333–341. doi:10.1001/archotol.1969.00770030335014
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