This paper describes the pattern of f2-f1 and 2 f1-f2 components at the output of the nonlinear hair cell mechanoelectrical transducer when the input consists of two sinusoidal signals. The mechanoelectrical transducer was represented by a second-order Boltzmann function. It is shown that some experimental observations, which have been cited to prove the existence of two discrete sources of distortion product otoacoustic emissions in the cochlea, can be produced by a single nonlinearity. These observations include the pattern of magnitude and phase 'notches' in the growth functions of the distortion product otoacoustic emissions when measured in the two-dimensional space of the amplitudes of the two primaries. A single saturating nonlinearity also explains the distinctive response of the distortion product otoacoustic emissions to the decreasing gain of the cochlear amplifier. A possible basis for the differences in distortion product otoacoustic emissions, which have been measured in humans and rodents, is discussed.