Suppression tuning characteristics of 2f1-f2 distortion product otoacoustic emissions

The 2f1-f2 distortion product otoacoustic emission (DPOAE) is suppressed by a third tone following a frequency selective pattern and outlining tuning curves which are generally similar to neural and psychophysical findings. The most effective suppressor tone lies between f1 and f2; less suppressive effects are produced by an added tone that lies in the 2f1-f2 site. The slope of iso-suppression curves is much steeper on the higher flank than on the lower flank of the suppression curve (respectively 100-115 dB/octave and 25-35 dB/octave). A suppression fine structure can be observed in the region of the tip especially for higher DPs probably connected with the fine structure of distortion products and with the instability of cochlear activity. A saturation point, around 70 dB or more has been evidenced on the growth rate functions. Continuous and interrupted suppressor presentation can induce some differences in the responses. Suppression of DPOAEs can provide a wider knowledge on active non-linear mechanisms in the cochlea, and on frequency selectivity also in a clinical context.