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 conditions, the duration (D) of a one-component on-frequency (M1; D(m1)-alone) 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 relative-duration conditions, the duration of one masker component was fixed at a relatively long value and the duration of the other component was varied (D(m1) > D(m2) or D(m2) > D(m1)). In the D(m1) > D(m2) condition, 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 threshold was frequently lower in the M1+M2 than in the M1-alone conditions, indicating psychophysical suppression. Further, masked threshold in the D(m2) > D(m1) condition was always higher than in the corresponding absolute-duration condition (D(m1)=D(m2)) having the same M1 duration, indicating masker enhancement. A two-stage neural model was proposed to account for these forward-masking data.