Does sound have momentum?

Soso said:

Does sound have momentum?

Well sometimes I just can’t a particular song out of my head, you know?

Yes

As I understand it, sound is just the movement of a medium, whether that is air, water, metal or anything else. If you stand near an explosion, you will feel a blast of air hit you as the shockwave reaches you. That wave is just a moving change in density of the medium, in this case, air.
Not sure if that counts as momentum, my guess is that it depends on your definition of it.

I have just been reading about the “third wave”, which is a new type of sound recently discovered in Helium4.

It is very weird.

http://www.physics.berkeley.edu/research/packard/current_research/schechter%27s%20web/page2.html

Kingy said:

I have just been reading about the “third wave”, which is a new type of sound recently discovered in Helium4.

It is very weird.

But not in a bad way.

Soso said:

Does sound have momentum?

Good question.

It depends at what scale you measure it.

Since the transmission of sound is a wave through some medium, with no resulting movement of the centre of mass, on the global scale the sound has zero momentum.

On the other hand at a smaller scale the sound wave does create a continually changing momentum in the parts of the medium it is travelling through.

And reviewing the first statement, unless the sound wave is perfectly reflected, there will be some transfer in energy resulting from the passage of the wave, so there may be some small change in momentum, unless the energy is entirely transferred to heat, in which case there will be change in momentum at the macroscopic scale.

Dunno, but sound is energy and it has velocity…

P=mv
E=mc^2

P=(e/c^2).speed of sound

Soso said:

Does sound have momentum?

Yes. See http://www.sciencedirect.com/science/article/pii/S0378437105008320

“Energy and momentum of sound pulses”
“The energy and momentum of three-dimensionally localized sound pulses are shown to be constant in time for propagation in fluids of negligible viscosity. Further, the energy always exceeds the product of the momentum and the speed of sound.”