Folds in the latest level, and the source's spectrum bars when it has them.
The latest raw level, 0..1 (clamped).
Optionalspectrum: readonly number[]The source's current spectrum bars, or nothing to synthesize bars from the level.
Returns to silence.
Smooths one audio source for display. Feed it the latest level (0..1) each animation frame, with the source's spectrum bars when it has them (an analyser tap); without them, bars are synthesized from the level (SynthesizeAudioBars). Pure: no Web Audio, no clock.