Speed of Sound

[jjunior]

Can someone confirm the following two points, are they correct?

1. speed of sound is greater in a denser medium
2. the lighter the molecule (eg. H2, as oppose to He), the faster it travels?

does this mean that speed of sound is greater in solid>liquid>gas medium, but within the gas medium, if the molecules make up the gas is less dense, the speed of sound is faster?
it just seems a little convoluted, can someone confirm it? thnx

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[athockey7]

speed of sound is not necessarily greater in denser medium... if the medium is in the same phase..

but besides that everything u said was right

 

[The_Sunny_Doc]

Speed of sound depends on two properties of the medium. The inertial properties ("heaviness", or density of the particles of the medium) and elastic properties (stiffness, or how fast the particles snap back to their original positions).

A stiffer medium will have its molecules bounce around much more quickly because they want to snap back to position right away, transmitting the sound wave faster through it. See this animation.

A "lighter" medium will also have its particles bouncing more quickly to transmit the sound wave. Think of making a wave with a length of hose vs a cotton string. It's much easier to get a wave going in a lighter material, which is less resistant to changing its motion.

Gases are less elastic vs solids and liquids because the molecules are so far apart, so they transmit waves more slowly compared to solids and liquids.

However, if you compare gases to other gases, some transmit sound more quickly than others. This is due to the inertial property that affects sound transmission. The "lighter" (less dense) gas particles will bounce around more easily, transmitting the sound wave faster.

 

[jjunior]

that makes sense, thnx!