Half a croissant, on a plate, with a sign in front of it saying '50c'
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Energy from Freeway Sound Barriers

Small, cheap acoustically driven generators to capture sound energy.
  (+7, -1)
(+7, -1)
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Hexagonal acoustic cells about the size of an egg (but of course open at one end) are built into the surface of a wall meant to block freeway noise. Each cell has a flexible back wall which operates as a microphone, generating just a trickle of current. The AC thus produced is converted to DC and hooked up in parallel with the other elements in its section of wall. I think there would be roughly 13 million cells per kilometer of sound barrier (wall is 4 meters high, each cell 3 cm diameter) so that a lot of tiny generators. The cells must be very cheap and durable, and the wiring kept to a minimum so as to avoid the expense of lots of copper. Have to do a cost-benefit analysis, eh?
Dog Ed, Aug 29 2001

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       How much energy could we expect these to produce, though? Why not just make this trendy and sell it as a wallpaper to partly power people's houses?
sdm, Aug 30 2001

       I think this idea would be better suited to daycares.
rapid transit, May 16 2003

       Don't forget that any energy that you extract from this will have to be reflected in larger energy usage by the cars. Also, sound energy from machinery is something like 0.7% (or is is 0.07%? small, anyway) of the total power of the system, so there's not much to extract.
willard_b_trophy, Mar 14 2004

       Use the standard steel bar and chip board barriers they put up in construction zones, but attach the bottom of the boards to a set of gears, which goes to a generator. As the boards flap back and forth, the generators get the power. You'll need less wiring, and the expensive bits can be stored beneath the road surface, where damages will be minimal.
ye_river_xiv, May 01 2007

       Sound energy is typically measured in picoWatts, so I doubt that the system would be cost-effective. I think [UnaBubba]'s heat collection would be (slightly) better, but then, what do I know?
neutrinos_shadow, May 01 2007

       //Have to do a cost-benefit analysis, eh?//   

       Yeah ...   

       //Don't forget that any energy that you extract from this will have to be reflected in larger energy usage by the cars.//   

       Why? I thought the noise was the result of wasted energy any way.   

       The neatest thing about this idea is that the little micropones would act as magnetic sound dampeners. It might be worthy for that alone.   

       And that is the end of my annotation of an idea that is six years old.
nomocrow, May 01 2007

       Mufflers would be prohibited, and you'd have to put straight pipes on you car and run it at full throttle all the time to maximize the effect. And turn up the stereo all the way, too. [+]
nuclear hobo, May 02 2007


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