The effect of contralateral stimulation on spontaneous acoustic emissions

Abstract

Subjects exhibiting spontaneous acoustic emissions (SAEs) were presented with wideband noise in the ear contralateral to that in which their SAE was being recorded. The SAE magnitudes were monitored while the noise was incremented in 5-dB steps. Some SAE components were markedly reduced with increasing contralateral stimulation while others appeared to be enhanced, despite frequency separations between components of less than 200 Hz. The effects were in the order of 3–10 dB, though occasionally greater, and the threshold for the SAE change was generally below the acoustic reflex threshold for that subject. The rms level of the ear canal noise in the ipsilateral ear was also monitored to ensure that none of the observations were a result of transcranial transmission of the stimulus. Pure tones were substituted for the noise in order to determine whether the effect was tuned; however no sharp tuning was observed.