Quantification of audiogram fine-structure as a function of hearing threshold.

We investigated the amount of fine-structure in the audiograms of patients with Menière's disease. Both ears (often an affected and an unaffected ear) were investigated. Data are presented from 39 ears of 21 patients with hearing thresholds varying from about 0 to 70 dB HL. The fine-structure was measured in the frequency range from 500 to 3500 Hz; this agrees with a part of the basilar membrane from 10 to 22.5 mm from the apex. The fine-structure was characterized by means of the number of peaks N(p) and the sum S(p) of the heights of all the peaks in an audiogram. From these quantities, we also determined average peak height H(p). We found a negative correlation between hearing loss and strength of fine-structure, i.e. the higher the thresholds the smaller N(p) and S(p) as well as H(p). Also N(p) and H(p) were correlated, i.e. the more peaks the higher the average peak height. The summated peak height S(p)=N(p)H(p) showed a strong dependence on the hearing loss. In cases of strong fine-structure, S(p) reached values around 200 dB.