The effect of acoustic reflex on contralateral suppression of transient-evoked otoacoustic emissions

Contralateral suppression of transient evoked otoacoustic emissions (TEOAEs) test evaluates the efferent auditory system. In this test، acoustic reflex is an important confounding variable. In recent years، application of this test is growing especially in children suspect to central auditory processing disorder. Therefore، the magnitude of influence of this confounding variable on the suppression of TEOAEs should be made clear. The aim of this study was to investigate the impact of acoustic reflex on contralateral suppression of TEOAEs. This research was performed on 39 normal-hearing adults of both sexes and of 18-26 years of age. Tests were used for the determination of interaural attenuation (IA)، acoustic reflex، TEOAEs and contralateral suppression of TEOAEs. TEOAEs amplitudes and their contralateral suppression were significantly higher in females and males respectively (p=0. 01). The amount of TEOAEs suppression before reflex activity ranged between 2000 to 3000 Hz. Activation of acoustic reflex significantly increased the magnitude of suppression in all frequency bands (p≤0. 01) and maximum suppression occurred in 500 to 1000 Hz. For achieving accuracy of clinical findings، clinicians should always use suppressant levels lower than the acoustic reflex threshold. It is recommended that different norms for males and females be used in contralateral suppression of TEOAEs.