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Location: UFOUpDatesList.Com > 1997 > Aug > Aug 8

Re: Skywatch: Re: silent engines

From: DRudiak@aol.com
Date: Thu, 7 Aug 1997 23:25:43 -0400 (EDT)
Fwd Date: Fri, 08 Aug 1997 09:58:55 -0400
Subject: Re: Skywatch: Re: silent engines

I know nothing of inherently silent aircraft engines, but there has
definitely been research in CANCELLATION of engine noise.  Strategically
placed microphones feed data into a computer, which outputs sound waveforms
to strategically placed speakers 180 degrees out of phase with the original
sound waves.  This causes sound cancellation through destructive
interference, a very old principle.

I think there has been work along these lines to produce a relatively quiet
(but not silent) helicopter.  In the civilian arena, the same idea has been
experimented with to get rid of  automobile mufflers, which decrease gas
mileage and engine power.

David Rudiak

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