Tiny periodic signals can be recovered from heavy noise via autocorrelation

Evidence

This works so well that tiny signals can be rescued from a lot of noise, as seen in figure 4.13. A pure noise signal and its autocorrelation are shown at the bottom. A noisy signal with a smooth periodic signal embedded appears at the top. The combined signal looks as ragged as the one at the bottom, which is pure noise. However, computing the autocorrelation reveals the hidden signal (top right). — Eric J. Heller, Why You Hear What You Hear- An…, 432

Categorization

• CANDY: A nicely counterintuitive fact: a signal that looks like pure noise can be perfectly recovered by autocorrelation.
• corroborated: 2 independent passages support this claim — Eric J. Heller, Why You Hear What You Hear- An…, 432
• XREF: connects to: Impulse velocity response serves as a ready-made autocorrelation; Autocorrelation discriminates echoes from genuine distinct sounds.; Temperature autocorrelation reveals weather’s daily and seasonal periodicities. (+6 more)

Broader Connections

• A threshold-spike autocorrelation model transforms auditory filter output into a periodic spiketrain. #exemplifies (0.85)