Tohoku J. Exp. Med., 2003, 200 (3)

Effects of Contralateral Noise on the Measurement
of Auditory Threshold

TETSUAKI KAWASE, MASAKI OGURA, TOSHINORI SATO,
TOSHIMITSU KOBAYASHI and YÔITI SUZUKI¹

Department of Otolaryngology, Head and Neck Surgery, Tohoku University Graduate School of Medicine, Sendai 980-8574, and
¹Research Institute of Electrical Communication, Tohoku University, Sendai 980-8577

It is well known that sound presented in the contralateral ear can elicit the activity of the olivocochlear (OC) efferent. In the present study, the effects of the addition of contralateral noise on the psychophysical measurements of auditory thresholds were investigated in human subjects with normal hearing. The results obtained in the present study indicate that the addition of contralateral noise at a level of only 20 or 30 dB sound pressure level (SPL) may cause a significant elevation of the auditory threshold in the mid-frequency area (usually 2-3 dB). When the level of contralateral noise was elevated, the elevation of the auditory threshold tended to be larger and the affected frequency area became wider. Although other factors that elevate the auditory thresholds, such as cross-talk effects and the acoustic reflex of the middle ear muscles, may be involved in the above-mentioned paradigm, especially when higher levels of contralateral noise are used, it is important to know the degree of OC-mediated threshold elevation in usual audiometric measurement.

keywords —— audiometry; masking noise; olivocochlear efferent; suppression

© 2003 Tohoku University Medical Press

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Tohoku J. Exp. Med., 2003, 200, 129-135

Address for reprints: Tetsuaki Kawase, Department of Otolaryngology, Head and Neck Surgery, Tohoku University Graduate School of Medicine, 1-1 Seiryomachi, Aoba-ku, Sendai 980-8574, Japan.

e-mail: kaw@mail.cc.tohoku.ac.jp