An impulse determines the average power deliverable at any frequency interval

Evidence

Average power theorem: The power that can be supplied to a system by sinusoidal driving at a point, averaged over a frequency interval Δf, is constrained by the response to an impulse at that point, up to a time τ = 1/Δf after the impulse. The smoothed power spectrum (smoothed over a region of width Δf surrounding any given frequency) is unaffected by any echoes arriving after this time. — Eric J. Heller, Why You Hear What You Hear- An…, 1091

Categorization

• DEFINE: Formal statement of the average power theorem — the chapter’s load-bearing concept.
• XREF: Connects to the uncertainty principle analogy and to Feynman’s path integral / early-time physics ideas.