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In Reply to: Re: speakers that lift a skirt up??? posted by Steffanie on April 29, 2007 at 12:49:37:
By any reasonable meaning of speakers you are correct, it is impossible. Sound is fluctuating air motion, not one-directional. You can make clothing flutter, but not push it up or down or sideways. Even fluttering is difficult; you would have to stand right next to the speaker (in the "near field") and run very low frequencies very loud.To stretch a point, there is something called "acoustic levitation" - that's the closest I know of. It requires pressure variations so extreme I would hesitate to call them "sound" - and I have spent a career studying the acoustics of jet engines. Technically, you can get a small one-directional force when the pressure excursions are so large that they exceed the atmospheric pressure, so the equations of motion become significantly nonlinear. That means 194dB sound pressure level. A qualified THX movie theater can produce about 104dB, so you would need a billion times as much power as the movie theater. I don't think any ordinary house would survive the sound, certainly not any living person or animal.
The biggest thing I've seen levitated was one of those foam plastic packing peanuts, and it took an industrial-strength horn driver confined to a 3" diameter pipe to do it. The pipe resonances boosted the sound level, but the horn driver was on the verge of going up in smoke.
Somewhere - probably on u-tube - there is an episode of Mythbusters where they tried to blow the roof off a car with a giant woofer. In fact they made a 4-ft diameter metal cone, and drove it from the driveshaft of the engine (100 horsepower is 74,600 watts ...). The "speaker" self-destructed but the rest of the car was pretty much untouched. This is nowhere near enough sound level to make nonlinear acoustics.
I think the BF owes you a nice dinner and a Jane Austen movie. :^)
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Follow Ups
- Re: speakers that lift a skirt up??? - Paul Joppa 12:09:47 04/30/07 (1)
- Re: speakers that lift a skirt up??? - Steffanie 17:38:44 04/30/07 (0)
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