ASA 125th Meeting Ottawa 1993 May

5aPP14. The effects of notched noise on detection of amplitude modulation of narrow-band noise.

Elizabeth A. Strickland

Neal F. Viemeister

Dept. of Psychol., Univ. of Minnesota, 75 E. River Rd., Minneapolis, MN 55455

The temporal modulation transfer function for narrow-band noises does not appear to change substantially as a function of carrier frequency, although auditory filter width increases with frequency. One possibility is that listeners always listen at high frequencies, where auditory filter width is relatively broad, regardless of the carrier frequency. To examine this possibility, detection thresholds for sinusoidal amplitude modulation were measured for a low- and a high-modulation frequency as a function of frequency location of a narrow-band noise carrier, in the presence of low-pass, high-pass, or notched noise. Results indicated that high-pass and notched noise produced a nearly identical increase in thresholds, while low-pass noise had little effect. The effect of the noise was similar for all carrier frequencies, suggesting that listeners were not listening at high frequencies in all conditions. The similarity of the effects of high-pass and notched noise indicate that listeners may use spread of excitation, when available, to aid in detecting modulation of narrow-band signals. [Work supported by NIDCD Grant No. DC00683.]