Time-frequency uncertainty applies both to the sound source and the analysis window.

Evidence

When making a sonogram, we encounter the time-frequency uncertainty principle twice: once for the source, and once for the analysis. The source will typically have its own characteristic time or times over which it changes in significant ways. The sonogram analysis performs separate frequency analysis at different times, but it must choose the length of the window over which it does each analysis. (The time axis on the sonogram is really the time at the center of an interval or “window” of time over which the sound is sampled and analyzed.) — Eric J. Heller, Why You Hear What You Hear- An…, 445

Categorization

• DEFINE: Clarifies that the sonogram’s time axis is actually window-center time, not instantaneous time.
• XREF: Mirrors Heisenberg’s uncertainty principle in physics; a cross-domain parallel the reader likely appreciates.