Power spectra capture component amplitudes but discard phase information

Evidence

The relative phase of the two components affects the shape of the wave resulting from adding them (see the two cases on the left, for a relative phase of 0° and 97°), but the power spectrum (right) remains the same. That is, the power spectrum is insensitive to the relative phase of the partials. — Eric J. Heller, Why You Hear What You Hear- An…, 339

Categorization

• DEFINE: Defines the key property that a power spectrum erases phase; fundamental to understanding harmonic analysis.