The onset of a noise [0.9-2.1 kHz, 55 dB SPL [sound pressure level] (A weighted)] preceded that of a buzz [100 Hz, 0.5-3.0 kHz, 70 dB SPL (A weighted), 500 ms] by -10 to +80 ms and both terminated simultaneously. Eight adult human subjects discriminated among noise-lead times in an oddity task. In separate sessions, they labeled singly presented stimuli with either of the 2 responses: no noise or noise. The results were highly similar to those reported for the categorical perception of synthetic plosive consonants differing in voice-onset time. On the average, discrimination was best across a noise-lead-time boundary of about 16 ms, where labeling also shifted abruptly. These results and those of categorical perception, generally, were interpreted in terms of Weber''s law as applied to a single component within a stimulus complex. Categorical perception of sounds is not unique to speech and may be a general property of sensory behavior.