Comparison of frequency discrimination thresholds for complex and single tones in chinchillas

Frequency discrimination thresholds were measured from five chinchillas for harmonic tone complexes having a fundamental frequency of 250 Hz. Stimuli consisted of the fundamental frequency and the second through 10th harmonics with individual components added in either cosine phase or random phase. In general, thresholds were independent of overall level for sound levels between 47 and 77 dB SPL, and there was no difference in thresholds observed between cosine-phase tone complexes and random-phase tone complexes. Discrimination thresholds were also obtained for a single 250-Hz tone for comparison with complex tone thresholds. Similar to data reported in human subjects, thresholds in chinchillas for tone complexes were lower than thresholds obtained using a single tone, although chinchillas required a larger frequency difference than human listeners. The results suggest that the mechanisms of frequency discrimination of complex tones are similar between chinchillas and human listeners.