Filter shapes for brief signals as a function of preceding stimulation

Abstract

The threshold for a brief probe tone in a broadband noise was measured as a function of probe frequency (1 or 4 kHz) and masker level (0–40 dB spectrum level). The probe was always presented 2 ms after the onset of the masker, and the masker was preceded either by silence, or by a precursor with the same spectrum and level as the masker. For each subject there were some conditions in which probe threshold was higher with no precursor than with a precursor (overshoot), and some conditions in which probe threshold did not differ with the presence of a precursor. Filter shapes for the same brief probes were then measured using the notched noise method. The probe was always presented with a 2-ms delay from the onset of the notched-noise masker. The masker was preceded by silence or by a precursor. The probe level was set 10 dB above the threshold measured for a given condition in the overshoot experiment. A comparison will be made of filter shape and the presence or absence of overshoot. [Work supported by NINCDS.]