Auditory filter shapes were measured in eight male volunteers with normal hearing, using a notched-noise forward-masking paradigm and a signal frequency of 4 kHz. The measurements were made under three conditions: after listeners had taken eight doses of three 320 mg aspirin tablets every six hours; after an identical schedule of placebo ingestion; and one week after testing in the first two conditions had been completed. Half of the listeners did the placebo condition first, and half did the aspirin condition first. Aspirin and placebo were administered double-blind, and testing took place approximately one hour after the last dose. Filter shapes were significantly broader in the aspirin condition than in the placebo and post-test conditions, indicating that even a modest dose affects auditory frequency selectivity. Two-point measures of growth of masking did not differ significantly between conditions.