Nonmonotonic behavior of distortion product 2f1-f2: psychophysical observations.

A detailed study was made of the amplitude and phase characteristics of auditory distortion product 2f1−f2 in the neighborhood of an amplitude minimum. For f2=1.0, 1.2, and 1.4 kHz, f1 was varied from 0.68⋅f2 to 0.88⋅f2, and the (equal) intensity of the two primary tones was varied from 50 to 70 dB SPL. For the one subject investigated, the ampltiude of the 2f1−f2 distortion product exhibited a single minimum in the portion of the f1/f2 versus intensity plane explored. The value of f1/f2 at the minimum was 0.8 and was roughly constant for various frequencies of f2. The primary‐tone amplitude at the minimum decreased with increasing f2 from 60 dB SPL at 1 kHz to less than 50 dB SPL at 1.4 kHz. The 2f1−f2 phase in the neighborhood of the null was complicated. It changed abruptly at the minimum, it changed more rapidly with f1/f2 at primary‐tone intensities below the null than above, and it changed slowly with primary‐tone intensity at f1/f2 ratios both below and above the null. Therefore, a complete circuit...