SISI test and adaptation. II. Subjects with conductive hearing defects.

The effect of adaptation of the ear on the SISI test was studied at 500 Hz and 2000 Hz in 43 patients with chronic otitis and in 20 patients with otosclerosis. The mean adaptation was slightly over 10 dB, except in the otosclerosis group at 2000 Hz, for which the value was nearly 20 dB after continuous stimulation at 20 dB SL for 3 min. The mean SISI values ranged from 15% to 31% in the preadaptation tests and from 9% to 31% in the postadaptation tests. The scatter of the pre-and postadaptation SISI scores was wide, making statistical treatment of the results difficult. In the total material 22% of the values at 2000 Hz were positive according to Jerger's classification, and 32% were questionable. Adaptation slightly reduced the proportion of positive values, but there were changes towards both higher and lower levels in the cases of chronic otitis, while all the otosclerosis changes were diminutions.