Passive cavity resonance can amplify a drive without altering its motion

Evidence

The vocal folds are a high-impedance drive; their motion is almost unmodified by any feedback from the vocal tract. This fact is perhaps the seat of the source-filter confusion: if the drive (vocal folds) do not respond to feedback from the vocal tract, how can the latter be anything but a filter? The fallacy of this statement is the essence of resonance as discussed in many places in this book: passive amplification is possible, coaxing a drive that is anyway wasting most of its power to put out more power in certain frequency ranges, without actually changing anything the drive is otherwise doing. — Eric J. Heller, Why You Hear What You Hear- An…, 1677

Categorization

• DEFINE: Clarifies what resonance fundamentally is: passive amplification that coaxes more power output without changing the drive’s behavior.
• XREF: Connects to how the question of why we hear what we hear — the source-filter debate over the voice — also recurs in earlier chapters on walls and speaking trumpets. — connects to: Resonance requires confined old amplitude returning in phase with fresh drive amplitude; Driven systems settle to the drive frequency, responding weakly, not their natural one; Steady driven motion oscillates at the drive frequency, never the natural one (+2 more)
• corroborated: 2 independent passages support this claim — Eric J. Heller, Why You Hear What You Hear- An…, 1677

Broader Connections

• A resonant cavity can isolate a single frequency from complex sound. #expands (0.75) — Schafer, Murray R, The Soundscape- Our Sonic Environment…, 920