Use of performance-intensity functions for diagnosis.

Performance-intensity (PI) functions for phonetically balanced (PB) word lists were obtained for a group of normal listeners (27 ears), and for two groups of patients with cochlear (89 ears) and retrocochlear disorders (eight ears). Listeners with normal hearing or cochlear disorders exhibited mild to moderate reductions in discrimination score as the speech level was raised above the PB maximum. In contrast, patients with retrocochlear disorders showed a pronounced rollover phenomenon, characterized by a rapid decline in performance as the speech level was raised above the maximum discrimination score.