Is my understading of speed of sound correct?

[m25]

Here's the way I understand how the speed of sound works. Can you guys tell me if it's correct?

Speed of sound is affected by both density and elasticity. Less dense the given medium is, faster the sound travels, and more elastic the medium is, the faster the sound travels.

The effect of elasticity becomes more significant when the medium changes phases. So since solid has more elasticity than liquid, and liquid more than gas, the speed of sound in increasing order is gas<liquid<solid.

However, within the SAME phase, the effect of density becomes more significant. So for example, speed of sound will travel faster in a solid with lower density than a solid with a higher density.

Are these statements correct?

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[Shirafune]

Not sure about elasticity, but sound travels faster in denser objects.

 

[labqi]

If I recall correctly....v = sqrt (intermolecular forces / density )

With that said, the stronger the IMF (I.e solid) the faster the sound wave travels.


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[justadream]

Not sure about elasticity, but sound travels faster in denser objects.

I thought sound travels SLOWER in denser objects.

 

[Shirafune]

I thought sound travels SLOWER in denser objects.

AAMC 7 #22, if you've taken this test yet, directly supports what I said. Sound, in general, does travel faster in denser objects. What labqi said is the true relationship for determining the speed of sound.

If I recall correctly....v = sqrt (intermolecular forces / density )

With that said, the stronger the IMF (I.e solid) the faster the sound wave travels.

And I think you will agree that solids which have stronger IMF are typically more dense.

 

[justadream]

@Shirafune
Yes, I agree that speed of sound in:

solids > liquids > gas

which was why I was somewhat surprised to find the equation in TBR (or Physics Flashcards - possibly both - I can't remember) that says speed of sound decreases as speed increases.

http://en.wikipedia.org/wiki/Speed_of_sound

It's one of those things I just memorize.

I haven't done AAMC #7 yet (gonna do it in a few days!) but I'll look at it soon.

 

[The Brown Knight]

while the inverse relationship between speed and density is true for same phases, you need to use the Bulk Modulus to account for the speed in different phases. I think that's what you mean by elasticity, am I right?
With bulk modulus, it's the compressibility vs. incompressibility of the material that determines the speed of sound. The less compressible the material, the greater the bulk modulus and the faster the sound speed in that material.
I think the equations were like this: v = sqrt(Bulk modulus/density) and Bulk modulus = -pressure / fractional volume change

 

[type12]

Elasticity is your ability to go back to your original state, your ability to snap back after you've been distorted (think of water vs rubber band); think of density like inertia, as in your resistance to change shape. So, if you don't change shape, you're not going to move any waves through; if you do change shape, your ability to go back and is important because how is that any different than not changing shape? You need that oscillation, or else there is no wave. You've changed shape, and if you don't go back, no wave can go through.

So, you want easy to change, and easy to snap back. A solid is the most difficult to change shape, but it's elasticity is so awesome that it doesn't matter.