It has previously been reported [Smoorenburg, J. Acoust. Soc. Am.52, 615 (1972)] that for some stimulus conditions the psychophysically observed distortion product2f1 − f2behaves nonmonotonically. As either the frequency or the intensity of the primary tones is changed, the amplitude of the distortion product goes through an abrupt null and the phase goes through a sudden shift. We have observed a similar effect in a non‐linear model of the basilar membrane. The basilar membrane is modeled as a 175‐section transmission line, and nonlinearities are introduced into the viscous damping term of each section [Hall, J. Acoust. Soc. Am.53, 324 (1973); Kim, J. Acoust. Soc. Am.53, 324 (1973)]. In the model, the nulls are caused by standing waves at frequency2f1 − f2produced by reflections from the basal end of the membrane. Primary‐tone frequencies for which the nulls occur can be determined analytically [Schroeder, J. Acoust. Soc. Am.53, 429 (1973)]. If the same mechanism is operative in humans, then psychophysical investigation of these nulls should provide information about mechanical properties of the basilar membrane.