Manipulations of the duration and relative onsets of two-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 (M_x; D_mX-alone) or off-frequency (M₂; D_ml-alone) masker or the common duration of a two-component masker (D_mX = D_ml) 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_mX D_ml or D_ml D_mX). In the D_mX D_ml condition, masked threshold decreased as the duration of D_ml was increased. In the D_ml D_mX conditions, masked threshold increased and then decreased slightly as the duration of D_mX was increased. Masked threshold was frequently lower in the M_x+M₂ than in the Af_ralone conditions, indicating psychophysical suppression. Further, masked threshold in the D_m2 D_mX condition was always higher than in the corresponding absolute-duration condition (D_mX= D_ml) having the same M_x duration, indicating masker enhancement. A two-stage neural model was proposed to account for these forward-masking data.