Effects of temporal primary-tone arrangement on DPOAE properties in humans Free

Distortion-product otoacoustic emissions (DPOAEs) emerge as a by-product of the nonlinear amplification of sound waves in the cochlea when presenting two tones of frequencies f₁ and f₂. According to a widely accepted model, DPOAEs comprise two main components, which can be separated in the time domain using short stimulus pulses. The present study utilized two acquisition paradigms with different primary-tone arrangements, denoted as SP-f₁ and SP-f₂, to investigate the nonlinear-distortion component arising near the f₂-tonotopic site on the basilar membrane. In SP-f₂, a conventional paradigm, the f₁ tone was presented for 25 ms, whereas the f₂ tone was switched on 5 ms after f₁ onset for frequency-dependent durations between 3 and 11 ms to elicit the DPOAE. SP-f₁ interchanged the temporal arrangement and durations of the primary tones. DPOAEs were recorded at eight frequencies (f₂ = 1 – 8 kHz; f₂/f₁ = 1.2) and five primary-tone levels L₂ = 30 – 70 dB SPL in 56 normal-hearing ears from 33 subjects. Comparison between the corresponding DPOAE responses revealed significantly larger amplitudes and shorter latencies of the nonlinear-distortion component for SP-f₁, i.e. when the f₁ short pulse triggers DPOAE generation.