Contralateral frequency-modulated tones suppress transient-evoked otoacoustic emissions in humans

In order to test the sensitivity of the human medial olivocochlear bundle (MOCB) to stimulus frequency fluctuations, changes in transient-evoked otoacoustic emission (TEOAE) amplitude induced by frequency modulated (FM) tones were measured in 18 normal-hearing subjects. The results revealed that TEOAE amplitude was reduced by contralateral FM tones at 40 dB above pure-tone threshold, with significant influences of both modulation rate (MR) and modulation depth (MD). This finding is discussed in the light of other recent results indicating amplitude fluctuation and frequency bandwidth effects in MOCB activation in humans.