Responses of fibers in the cat's auditory nerve to the cubic difference tone.

Recordings were made of discharges in single fibers of the cat’s auditory nerve using single‐tone and two‐tone signals of varying frequency. The frequency of the single tone was varied stepwise from the fiber’s best frequency to about 1.7 times this value. One component of the two‐tone signal was varied in exactly the same manner while the frequency of the other was increased in such a way that the frequency of the cubic difference tone (CDT, 2f1−f2) generated within the auditory system was kept constant at the fiber’s best frequency. Responses in terms of discharge rate and period histograms were collected for both signals. The difference in spike rate between the response to the single tone and to the two tones could be ascribed to the CDT and was used to estimate the CDT level as a function of the signal level and frequency. It turned out that the CDT level relative to that of the primaries is about 15 dB smaller for frequencies beyond 10 kHz than for lower frequencies, and slighly decreasing for an in...