Stimulus-based limitations on the discrimination between different temporal orders of tones.

Listeners' abilities to discriminate the order of two tones, of frequency 500 Hz and 500 Hz + delta f, separated by less than 5 ms, were measured in terms of threshold durations (T) for the tones. The experiment was repeated for values of delta f between 5 and 160 Hz. The relation of the duration threshold to delta f was well-described by the reciprocity equation, delta fT = K, for K = 0.16. This reciprocity corresponds to a constant overlap of the main lobes of the power spectra for the tones of about 70%-80%. Addition of a trailing context tone severely degraded the ability to discriminate temporal order, increasing the value of the reciprocity constant to approximately K = 1.8. The primary effect of the context tones was to increase the duration required for accurate discrimination, rather than to impair actual frequency resolution. Implications of these results for speech perception are discussed.