Effects of non‐simultaneous modulated maskers on amplitude‐modulation depth discrimination.

Abstract

Wojtczak and Viemeister [J. Acoust Soc. Am. 118, 3198–3210 (2005)] demonstrated that detection thresholds for amplitude modulation (AM) can be increased in the presence of an AM forward masker. In the present study, the effects of forward‐masking on AM detection thresholds were extended to AM processing for easily detectable (suprathreshold) AM modulation depths by measuring the effects of nonsimultaneous AM maskers on AM modulation depth discrimination limens (AM DLs). Signal AM DLs were measured for a range of standard modulation depths. In one experiment the temporal delay between the masker and signal was varied. Consistent with the effects of AM forward maskers on AM detection thresholds [Wojtczak and Viemeister (2005)], the effects of the non‐simultaneous AM maskers on AM DLs were greatest for short masker‐signal delays. In another experiment, the masker‐signal delay was fixed, the signal modulation frequency was fixed, and the modulation frequency of the non‐simultaneous masker was varied. AM DLs for the signal were usually greatest when the signal modulation frequency was equal to the masker modulation frequency. The results of these experiments suggest that non‐simultaneous AM maskers can affect suprathreshold AM processing but non‐simultaneous AM maskers become less effective as the modulation depth of the standard increased.