Dissipation of sound energy

[phelpio]

I was thinking about how all energy normally degrades into heat, such as in the resistance of electric current, friction in kinetic energy or how light is absorbed into a surface and warms it.

 

Does this happen with sound?

 

Of course i googled it and found this answer page: Here

 

Some people have stated that sound energy keeps spreading out uniformly to infinity, some people think that it will degrade to a form of low level heat energy.. none state any references..

 

But..

 

If a 2000w speaker was placed within a bottle in a vacuum so no sound energy can escape, will the sound eventually heat the surrounding area by some method? or would this sound continually spread out and just become 'background noise'?

 

This would mean that all sound that has ever been generated is still around, uniformly spread out..

 

Or... could the molecules moving as a sound wave collide and cancel each other out? e.g. two cars hitting each other head on at 30mph and coming to a dead stop.

 

but the caloric theory states that energy cannot be created or destroyed..

 

Also as sound is a mechanical pressure wave would the molecules through the medium the wave is travelling in would be subject to friction and create heat?

 

 

I'm confused!!!

 

 

Phelpio

[Externet]

Sound energy decays into heat.

 

That 2Kw speaker in vacuum... nothing escaped nor reached the surroundings because never emitted sound without air. It just vibrated and the mechanical friction became heat.

[DrRocket]

What is thermal energy ? It is juat the kinetic energy of the random motion of molecules.

 

What is sound ? It is the effect of motion of gas molecules in a somewhat organized linear oscillatory motion.

 

So as a sound wave is continually reflected and refracted by bouncing around and contacting solid objects and as the molecules collide with other molecules, the motion becomes more and more random until it can finally be classified as thermal energy.

Edited November 6, 2011 by DrRocket