Glenis R. Long
Dept. of Audiol. and Speech Sci., Purdue Univ., West Lafayette, IN 47905
Carrick L. Talmadge
Lauren Shaffer
Purdue Univ., West Lafayette, IN 47905
Synchronous evoked otoacoustic emissions (SEOAEs) provide evidence that the impedance of the human auditory system varies systematically with frequency. Frequency-independent acoustic input to an intact human auditory system leads to regular patterns of maxima and minima in the acoustic stimulus measured in the ear canal. The pattern of SEOAEs is also seen in changes in the level of distortion product otoacoustic emissions (DPOAEs). Contralateral acoustic stimulation moves the entire pattern of SEOAEs up in frequency. Monitoring SEOAEs or DPOAEs at one frequency in the presence of contralateral stimulation would thus lead to a level increase at some frequencies and a reduction at others. This pattern was observed in a subject with elevated contralateral acoustic reflexes, making it probable that the effect is generated by efferent innervation. The implications for the use of oto-acoustic emissions to evaluate efferent function will be discussed together with the impact on cochlear models. [Work supported by NIDCD and DRF.]