Magnitude of medial olivocochlear reflex assayed by tone-burst-evoked otoacoustic emissions: reliability and comparison with click-evoked emissions.

The purpose of this pilot study was to evaluate the magnitude of the medial olivocochlear reflex (MOCR) estimated by the reduction in tone-burst evoked otoacoustic emissions (TBOAEs) measured at three levels and at three frequencies in response to fixed contralateral white noise. Results were compared with commonly used click-evoked otoacoustic emissions (CEOAEs). TBOAEs and CEOAEs, with and without contralateral 60 dB SPL white noise, were measured in response to stimulation at 55, 65, and 75 dB peSPL. In each subject, the set of measurements was performed twice. Of particular interest were the MOCR and its repeatability. 15 normally hearing persons (13 women, average age 32.3 years, SD = 8.1). For both CEOAE and TBOAEs, the reliability of the MOCR was much better for broadband measurements than for half-octave-band filtered estimates. At the same time, the reliability of MOCR in half-octave bands was higher for TBOAEs than for CEOAEs, especially at 2 and 4 kHz. For general applications where broadband MOCR is of interest, the highest magnitude and reliability is provided by CEOAEs. However, TBOAEs may be better if a particular frequency band is of interest.