SUPPRESSION OF HUMAN ACOUSTIC DISTORTION-PRODUCT - DUAL ORIGIN OF 2F(1)-F(2)

In order to explore the origin of acoustic distortion product (DP) in the ear canal, the effect of the level and the frequency of the suppre ssor tone on the level of the DP was investigated. The results broadly support previous studies in showing that, with increasing suppressor level, the DP level shows an initial relatively stable plateau or grad ual decline? followed by a rapid decline. The shape of the human iso-s uppression contours derived from these ''suppression-rate'' curves was found to depend upon the size of the iso-suppression criterion. Low-l evel suppressor tones close in frequency to 2f(1) - f(2) were effectiv e at suppressing thr DP by up to 3 dB in subjects where the distortion frequency fell at a region of strong stimulus frequency re-emission. It is probable that contributions from the DP frequency region, as wel l as components from the primary frequency region, make up the ear can al measured DP. With a 6-dB iso-suppression criterion, suppresser tone s in the primary frequency region suppress DP most effectively. (C) 19 96 Acoustical Society of America.