The study investigated the ability to detect and discriminate frequency glides under a variety of experimental conditions. The subjects distinguished between a comparison signal that either was level in frequency or was swept across a fixed frequency span, and a target signal that changed more in frequency than the comparison signal. Tone durations were 50 and 400 ms. Nominal center frequencies were 0.5, 2, and 6 kHz; actual center frequencies were varied randomly, or roved, over a range equal to 0.1 times the nominal center frequency. Up- and down-glides were used. The transition span of the comparison signal was either 0, 0.5, 1, or 2 times the equivalent rectangular bandwidth of the auditory filter at the nominal center frequency. Discrimination thresholds were obtained for all combinations of center frequency, direction, and span. Overall, thresholds expressed as delta Hz/ERB varied little as a function of center frequency. Glide duration had no effect on discrimination. The 50-ms down-glides were more difficult to detect than the 50-ms up-glides; otherwise, the effect of direction was not significant. With the exception of the 50-ms down-glides, detection/discrimination thresholds were similar for the 0-, 0.5-, and 1-ERB transition spans, but increased significantly for the 2-ERB span. The absence of significant variation across frequency supports a place mechanism for the detection of frequency change in gliding tones, based on the detection of changes in the excitation pattern. An excitation pattern model cannot account for the asymmetry noted for glide detection, however.

Two experiments were performed to investigate subjects' ability to detect and discriminate 50-ms up-glides in frequency in several different conditions. In the first experiment, the subjects indicated which of two signals increased more in pitch. The comparison, or standard signal, was a sinusoid which increased in frequency by either 0, 250, or 500 Hz. Center frequencies were 0.5, 1, 2, 4, and 6 kHz. Discrimination thresholds were obtained in both nonroved and roved conditions. In the roved condition, the actual center frequencies of the signals were varied randomly over a range equal to 0.1 times the nominal center frequency. The second experiment was the same as the first, except that the standard signals were swept over a frequency range equal to 0.5, 1, and 2 times the equivalent rectangular bandwidth (ERB) of the auditory filter at the nominal center frequency. Discrimination thresholds expressed as delta Hz/ERB varied little as a function of center frequency as long as the frequency transition of the standard was a constant proportion of ERB. In addition, discrimination thresholds did not vary significantly as a function of the frequency extent of the standard when the extent was one ERB or less, but doubled when the extent was two ERBs. The relatively small amount of variation in threshold across center frequency and the pattern of variation across different standard transitions supports a place mechanism of frequency coding for these signals based on the detection of changes in the excitation pattern.