The medial olivocochlear reflex (MOCR) is a vital auditory mechanism where medial olivocochlear efferents suppress outer hair cell (OHC) movement. Contralateral acoustic stimulation is known to reduce the level of otoacoustic emissions (OAEs) induced by OHC activity. While white and broad-band noise are common contralateral stimuli, the optimal noise type for OAE suppression remains unclear. This study investigated the impact of square wave contralateral stimulation on distortion product otoacoustic emission (DPOAE) levels, identifying the influential frequencies. We measured DPOAE level changes in normal-hearing subjects (20s) when a square wave (10–300 Hz, ∼60 dB SPL) was used as a contralateral stimulus. Given that square waves comprise a fundamental frequency and various odd harmonics, complex waves incorporating these frequencies were also applied as contralateral stimulation. Results showed that DPOAEs were most effectively suppressed by a 100-Hz square wave, particularly at lower primary tone sound pressures. DPOAEs were also suppressed by applying the complex waves; however, the amount of suppression decreased when specific low- or high-frequency components were removed from these complex waves. This suggests that both low- and high-frequency components of the contralateral stimulus may contribute to DPOAE suppression.
KOIKE et al. (Wed,) studied this question.