Fig. 2.

Typical process of analysis of waveform modulation. A 2024 Hz 10 μA electrical stimulus f_e, applied to scala media in turn 2, was paired with an acoustical stimulus f_a at 86 Hz, 88 dB SPL. The ear canal sound field, containing the EEOAE and the acoustical stimulus, was electronically high- pass filtered to remove most of the spectral energy at 86 Hz as well as its second and third harmonics. The resulting “raw” waveform (A), consisting of the EEOAE and contamination from higher level harmonic distortion of the acoustical stimulus, had spectral peaks (B) at f_e and the intermodulation sideband frequencies and at the harmonic distortion frequencies. Decontaminated EEOAE waveforms were extracted by either (1) subtracting the acoustical contamination from the raw waveform (steps C–E) or (2) reconstruction through inverse Fourier transform from the spectral components at F_e and sideband frequencies (steps F, G).