EFFECTS OF CONTRALATERAL ACOUSTIC STIMULATION ON SPONTANEOUS OTOACOUSTIC EMISSIONS

Spontaneous otoacoustic emissions (SOAEs) were measured in the ear can al of adult humans prior to, during, and following presentation of ton al and broadband stimuli to the contralateral ear. Tones were presente d at a fixed level at ten frequencies relative to the SOAE. Broadband noise was presented at eight levels, from 6 to 76 dB SPL. Shifts in SO AE frequency and amplitude were observed for some subjects, for some t one conditions. Frequency shifts were always positive, whereas amplitu de shifts were variable. No apparent pattern of tuning was seen, such that tones with a particular frequency relationship to the SOAEs induc ed greater changes in the SOAEs. Systematic changes in frequency and a mplitude of SOAEs were observed for increasing level of broadband nois e for all subjects. Results are discussed with respect to possible mec hanism(s) responsible for the alterations in SOAEs: Transcranial condu ction; the olivocochlear system; and/or the middle-ear reflex arc.