Top panel illustrates the acoustic waveforms of the standard click and chirp stimuli. The rising frequency chirp stimulus was constructed in a fashion similar to Fobel and Dau (2004) using a place-frequency map obtained from derived band CAP latencies obtained by Eggermont (1979). The bottom panel is the corresponding spectra. Inset is the instantaneous frequency (IF) of the measured chirp stimulus (thick line) and desired or theoretical IF (thin line).
CAP responses from one subject, evoked by either a click (left panel), chirp (middle panel), or reverse chirp (right panel) stimulus. Responses were obtained at 125, 105, and 85 dB pSPL.
Ratio of the amplitude of N1 obtained with the chirp stimulus relative to the amplitude of N1 obtained with the click stimulus for each subject. Data points above 1 indicate that responses obtained from the chirp stimulus were larger than those obtained with the click stimulus.
Average amplitude of N1 computed from all subjects for each signal level used in this study. The open circles represent the mean values for the chirp stimulus and the filled symbols indicate the values for the click stimulus.
Average N1 latencies computed relative to the N1 latency at 125 dB pSPL. Filled circles represent responses to click stimuli and filled squares are responses from chirp stimuli. Linear regression indicated a decrease in N1 latency (re 125 dB pSPL) of for the chirp stimulus as opposed to for the click stimulus.
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