Autocorrelation reveals a signal’s fundamental periodicity through periodic peaks.

Evidence

In the example of Figures 3.7d–e, the autocorrelation of a voiced speech signal has a peak corresponding to its periodicity. The autocorrelation function is periodic, showing maxima also for integer multiples of the fundamental period. — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 400

A special case of correlation is autocorrelation, where a signal is compared to itself in order to find the periodicity, or repeatability, of the waveform. In this case x(·) = y(·) in Equations (3.26a) and (3.26b). In the example of Figures 3.7d–e, the autocorrelation of a voiced speech signal has a peak corresponding to its periodicity. The autocorrelation function is periodic, showing maxima also for integer multiples of the fundamental period. — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 400

Categorization

• DEFINE: Explains autocorrelation as the tool for finding waveform periodicity, with the peak-multiple structure.
• XREF: Autocorrelation is the core of pitch detection in hearing research and music information retrieval (e.g., YIN algorithm).
• corroborated: 3 independent passages support this claim — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 400