Rectification of amplitude-modulated sinusoids with particular reference to a hair cell transducer function

We modelled the hair cell transducer function as an asymmetric saturating zero-memory rectifier, using the data of Corey and Hudspeth and developed a method for calculating the output spectrum of a rectifier when fed with the sum of two amplitude-modulated pure sinusoidal tones. We report theoretical results for the following two cases: (1) the input is a single carrier whose output is modulated by the sum of two sinusoids, and (2) the input is the sum of two carriers, each of which is amplitude-modulated by a single sinusoid. In case (2) the terms in the spectrum are various combinations of the four stimulus frequencies (two carrier frequencies and two modulation frequencies). Theoretical results are compared with the results of an experiment in which field potentials were recorded from the human scalp while one ear was stimulated with auditory waveform (1) and with auditory waveform (2) above. We analyzed the brain responses using high-resolution zoom-FFT, at a frequency resolution of 0.008 Hz