On the subject of muffling turbine pumps and the like, I'm curious if
anybody's investigated the idea of using a method of canceling out the
noise.  This involves a microphone to detect the offending vibrations,
an amplifier with circuitry to re-constitute those sounds 180 degrees
out of phase with the original, and speakers to play it back into the
area where you want the sound muffled.

The principle here is that a sound wave 180 degrees out of phase with
another identical sound wave will cancel itself out.  I don't know how
one would go about setting up to do this, but it's an intriguing idea.
Has anybody on the list worked with this technology or know much about
it?

Regards,
Dick Merchant,
Carlsbad, NM

 [ Noise-canceling headphones are available for aviators, which
 [ reduce the throbbing in the cabin of a propeller aircraft.
 [ This probably would work quite well to reduce the throbbing
 [ of a Roots blower on an air calliope; I don't know how it might
 [ perform with the broad-band noise of a turbine pump.  -- Robbie