an un-recordable sound-- update

["Mark Fischer" aguasonic]

Hi everyone,

So, having discovered my relationship with mathematics to be a little
rusty, I had to resort to actually /measuring/, instead of ballpark
guessing.

They run a bit faster than I had guessed. In a nice breeze, 49 blades
per minute with three-bladed mills gives you 16.3 Hz. Considering
these have a span as large as a football field, and that is really
amazing.

So, they are conceivably at the very lowest edge of human hearing.

I will continue to keep an eye out for ideal conditions. If I can
manage to get anything like a usable recording I'll post it.

Cheers,

Mark
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