Sound Intensity Loss Question

[justadream]

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Mcat-review says

"Sound attenuation is the greatest forsoft, elastic, viscous, less dense material. "


Why is attenuation (loss in intensity) greatest in LESS DENSE material? Seems counterintuitive.

 

[The Brown Knight]

I'll take a wild guess:
I would expect attenuation to occur if the molecules of the medium don't fully return to their original position after a compression (you're probably aware that sound waves travel by alternating longitudinal compressions and decompressions). In something like a gas, the compressions would involve large displacements, so maybe a greater chance for the molecules to not fully return to their original position in comparison to something like a solid.
You'll probably ask about attenuation in a single phase with differing densities, and for that I don't have much of a guess! Maybe someone else can give a better explanation?

 

[justadream]

@The Brown Knight

How about for other types of waves (not just sound waves)?

Would you expect increased attenuation with smaller density materials?

I think it would be the opposite for electromagnetic waves. Isn't that why lead is useful as protection when taking X-rays?

 

[Oh_Gee]

guy here says that
"There is a formula for attenuation in fluids which takes into account the density. I think that's beyond what MCAT tests but it is correct that higher density has lower attenuation (less losses in high density materials)."

http://forums.studentdoctor.net/threads/sound-attenuation.894679/


i also thought that sound would travel slower in more dense materials than less dense...
maybe the phase of the material matters. i know the sound travels faster in less dense air
but does sound not travel faster in denser solids than less dense solids?