Tangential question: Are there any sound meters that can actually measure down to 0 dB? The best I’ve seen specify 20 dB, which to me is still very audible.

(Note that, as the article mentions, 0 dB doesn’t mean “zero sound pressure”, but just “threshold of hearing”.)

Some laboratory-grade equipment probably.

> 0 dB doesn’t mean “zero sound pressure”

From the decibel definition, zero of anything is -∞ in dB_suffix scale.