The mechanical movement of outer hair cells is controlled by the medial olivocochlear efferent system. Otoacoustic emissions enable the evaluation of this system. Captured physiological responses in normal individuals may be reduced by the application of a noise in the contralateral ear, creating the suppression effect. The stimulus used to test the suppression effect can be a click or a "tone burst". The click stimulates a wide frequency range in the cochlea and can be presented in a linear or nonlinear way. The Otodynamics IL0 USB - V6 equipment allows the research of OAE suppression alternating linear clicks with and without noise. It is necessary to establish normal reference values before the equipment can be applied clinically. Objective: To determine the occurrence and magnitude of suppression of otoacoustic emissions evoked by transient stimulus in term and preterm newborns, using Otodynamics IL0 USB - V6 equipment. Method: The sample consists of 40 neonates, 5 days to 4 months old, who presented otoacoustic emissions at birth. The sample will be distributed in two groups: GI - made up of 20 full-term infants without risk indicators for hearing loss. GII - comprised 20 preterm infants who spent over five days in the NICU with risk of hearing impairment. Infants should be in natural sleep, positioned on mother's lap. Two probes are placed in the ear canal of the newborn: one will present linear clicks and the other broadband noise. Reducing the noise response will indicate the presence of suppression effect. The average of suppression effect will be established with and without noise and the groups will be compared and analyzed statistically.
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