Suppression effects for complex stimuli

A pulsation-threshold paradigm was used to evaluate suppression effects within complex stimuli. Stimuli were chosen to represent a continuum of spectral complexity ranging from sinusoids to complexes with one and two suppressors. Results indicate that suppression effects exist between the response to components of complex stimuli. For frequencies above a single suppressor, the suppression region is broad whereas below a suppressor, the region is relatively narrow. With two suppressors, little additivity of suppression is seen. When they are spaced closely, the response to the higher-frequency suppressor is reduced, presumably due to the low-frequency suppressor; this tends to diminish spectral contrasts despite considerable suppression at frequencies between the two suppressors. Enhancement of contrasts is greatest when suppressors are widely spaced and when both are presented at moderate levels (≤ 60 dB SPL). These data suggest that suppression may not play a simple role of “peak enhancement” in the peripheral coding of steady-state vowels.