Insect wingbeat sounds are an unavoidable byproduct of vortex-based flight

Evidence

Vortices are shed by insect wings moving through the air, but in this case the frequency is governed by a single vortex that forms with every beat of the wing. A side effect of those vortices is the sound we hear. No doubt for survival reasons, the insects would prefer not to make this sound announcing their presence, but they must, since the vortex forms the basis for their flight. — Eric J. Heller, Why You Hear What You Hear- An…, 1305

Categorization

• XREF: Directly serves my why-do-we-hear-what-we-hear question: insect buzz is causally tied to the aerodynamic mechanism of flight, not a chosen signal.
• SEED: An evolutionary-acoustics essay angle: why animals emit sounds they cannot afford to silence — acoustic tell-tales of essential mechanical functions.
• BMF: No — though insect sound-as-unavoidable-byproduct is a thematic echo, nothing here maps onto a specific plot device in my library.