Temporal integration functions of amplitude modulation detection and amplitude modulation depth discrimination

Previous studies (Lee and Green, 1994; Lee and Bacon, 1997) suggested that both AM rate and AM depth discrimination were influenced by the number of AM cycles, instead of the duration of stimuli. AM detection and AM depth discrimination (standard depth=0.1) were measured as a function of the number of AM cycles for modulation rates of 10, 20, 40, 80, 125, 160, and 320 Hz. Different numbers of modulation cycles were used for each modulation rate: 2, 4, or 8 for 10 Hz; 2, 4, 8, or 16 for 20 Hz; 2, 4, 8, 16, or 32 for 40 Hz; 2, 4, 8, 16, 32, or 64 for 80, 125, 160, and 320 Hz. The carrier was a broadband‐noise (10 kHz lowpass), and the carrier was either gated with the modulator or presented 250 ms earlier and 250 ms later than the modulator. The overall level of each presentation was randomized within 6‐dB range from 65 dB SPL. The results suggest that there might be different temporal integration processes for AM detection and AM depth discrimination. The pattern is different for lower and higher modulation rates. [Work was supported by NIDCD Grant No. R03 DC06605‐01.]