Most real sounds have autocorrelations that decay over time.

Evidence

Most sounds fall somewhere between white noise and perfect periodicity, often showing interesting structure in their autocorrelation. Their autocorrelation typically decays at longer times, indicating that the sound pressure at a given time is uncorrelated with the sound pressure far enough in the future. — Eric J. Heller, Why You Hear What You Hear- An…, 413

Categorization

• DEFINE: Characterizes typical sounds’ autocorrelation: decay at longer time lags.
• XREF: Relates to how much of the ‘meaning’ of sound lives in short time windows; connects to auditory attack/decay perception.