Latency-frequency functions extracted from: (1) narrow-band ACAP (Eggermont, 1979), (2) tone-burst ABR (Neely et al., 1988), (3) narrow-band ABR (Don-data, Don et al., 2005a), and a cochlear model (de Boer, 1980). On each latency-frequency function the fitting formula and the retrieved parameter values are indicated. Also included are the four data points (Table I) that are used for the curve fitting of the Don-data.
The Don latency-frequency function (Fig. 1) applied to a linear system. The calculated group delay, phase delay, and phase response are shown together with the corresponding equations.
Demonstration of how a broadband stimulus with a repetition rate of 20/s is obtained by taking the sum of a harmonic series of cosines with the frequencies . (From the harmonic series are shown the first three cosines followed by the cosines that are spaced by approximately half an octave). All cosines have equal amplitude and are given a phase delay in accordance with the values in Fig. 2 (Don-data).
Broad band stimulus with a repetition rate of 20/s obtained by adding together a harmonic series of cosines with the frequencies all with equal amplitude. Three different sets of phase delay values are used: (top, “modified click”) Phase delay=model delay (Fig. 2); (middle, “click”) phase delay ; and (bottom, “chirp”) phase delay=negative value of the model delay (Fig. 2).
Three different chirps calculated similarly to the broadband chirp in the bottom curve of Fig. 4, but based on a repetition rate of 90/s. The broadband covers the frequency range . From the original latency-frequency functions by Neely et al. (1988), de Boer (1980), and the Don-data shown in Fig. 1, the negative values of the corresponding phase delays are used for the calculations. The chirps are called: Neely et al. chirp, de Boer chirp, and Don chirp.
(a) Grand average ASSR wave forms at for the three chirps and the reference click stimulus after a recording time of . The calculated peak-to-peak amplitudes are shown for each wave form. (b) Grand average ASSR wave forms at for the three chirps and the reference click stimulus after a recording time of . The calculated peak-to-peak amplitudes are shown for each wave form.
Peak-to-peak amplitudes of the grand average ASSR wave forms [Figs. 6(a) and 6(b)] plotted vs stimulus level.
Derived-band ABR center frequencies and the corresponding observed wave V latencies for the Don-data . The latencies corrected by are shown in the last column, which also indicates that only the corrected latencies for the four lower frequency bands are used for the construction of the final latency-frequency function in Fig. 1.
For each stimulus condition (stimulus type and level), the number of subjects tested, the detection rate (in % and fractions), the detection time within (median and 5%–95% percentile), and the SNR at a recording time of (median and 5%–95% percentile) are shown.
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