MANIPULATIONS OF THE DURATION AND RELATIVE ONSETS OF 2-TONE FORWARD MASKERS

The effects of absolute and relative masker duration were investigated using one- and two-tone forward maskers. In the absolute-duration con ditions, the duration (D) of a one-component on-frequency (M1; D(m1)-a lone) or off-frequency (M2; D(m2)-alone) masker or the common duration of a two-component masker (D(m1)=D(m2)) Was varied. Masked threshold increased as duration increased in all three conditions. In the relati ve-duration conditions, the duration of one masker component was fixed at a relatively long value and the duration of the other component wa s varied (D(m1) > D(m2) or D(m2) > D(m1)). In the D(m1) > D(m2) condit ion, masked threshold decreased as the duration of D(m2) was increased . In the D(m2) > D(m1) conditions, masked threshold increased and then decreased slightly as the duration of D(m1) was increased. Masked thr eshold was frequently lower in the M1+M2 than in the M1-alone conditio ns, indicating psychophysical suppression. Further, masked threshold i n the D(m2) > D(m1) condition was always higher than in the correspond ing absolute-duration condition (D(m1)=D(m2)) having the same M1 durat ion, indicating masker enhancement. A two-stage neural model was propo sed to account for these forward-masking data.