MODULATION DETECTION BY NORMAL AND HEARING-IMPAIRED LISTENERS

In five normally hearing subjects and seven subjects with damaged coch leas, detection thresholds for sinusoidal frequency modulation (FM) an d amplitude modulation (AM) were measured using 1 s stimuli with a 500 Hz carrier frequency (Fc) at a 'comfortable' loudness (given by subje ct-dependent SPLs and SLs). The modulation frequency (Fmod) was 2 Hz o r 10 Hz. FM (but not AM) detection was poorer in the hearing-impaired group, especially when the hearing loss at Fe exceeded 50 dB. Fined ha d a different effect on FM and AM detection. The corresponding interac tion was essentially identical for the two groups of subjects. Previou s studies strongly suggested that normal listeners use mainly neural p hase-locking cues for the detection of FM when Fmod = 2 Hz, but mainly tonotopic cues when Fined = 10 Hz. The present results suggest that c ochlear damages reduce the usefulness of these two types of cues to an approximately equal degree.