SUPPRESSION TUNING CHARACTERISTICS OF 2F(1)-F(2) DISTORTION-PRODUCT OTOACOUSTIC EMISSIONS

The 2f(1)-f(2) distortion product otoacoustic emission (DPOAE) is supp ressed by a third lone following a frequency selective pattern and out lining tuning curves which are generally similar to neural and psychop hysical findings. The most effective suppressor tone lies between f(1) and f(2); less suppressive effects are produced by an added tone that lies in the 2f(1)-f(2) site. The slope of iso-suppression curves is m uch steeper on the higher flank than on the lower flank of the suppres sion curve (respectively 100-115 dB/octave and 25-35 dB/octave). A sup pression fine structure can be observed in the region of the tip espec ially for higher DPs probably connected with the fine structure of dis tortion products and with the instability of cochlear activity. A satu ration point, around 70 dB or more has been evidenced on the growth ra te functions. Continuous and interrupted suppressor presentation can i nduce some differences in the responses. Suppression of DPOAEs can pro vide a wider knowledge on active non-linear mechanisms in the cochlea, and on frequency selectivity also in a clinical context.