THE ROLE OF FREQUENCY RESOLUTION AND TEMPORAL RESOLUTION IN THE DETECTION OF FREQUENCY-MODULATION

The experiment investigated subjects' ability to detect short-duration changes in frequency. In an adaptive, 2AFC task, three normal-hearing subjects were asked to distinguish a sinusoidal signal that increased in frequency in a series of discrete steps from a standard that was i dentical except that its frequency increased essentially continuously. The signals were 60 ms in duration with center frequencies of 0.25, 0 .5, 1, 2, 3, 4, and 6 kHz. The smallest frequency increase between ste ps (FI) at which the stepped signal could be distinguished from the st andard was determined as a function of the number of steps in the sign al. As the number of steps increased and the step duration decreased, the Fl at first decreased and then reached a roughly asymptotic level. Eventually, however, at a certain number of steps, the FI increased r apidly. The data were analyzed using a model of auditory temporal reso lution that included a bank of bandpass filters, a nonlinearity, a tem poral integrator, and a decision device. The analysis yielded ERDs tha t ranged from 3.8 to 5.0 ms and did not change systematically with fre quency. Detector efficiency varied considerably, being greatest at 0.5 and 1 kHz, and declining at higher and lower center frequencies.