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# Physics/Spped of Sound waves

Question
Respected Sir, my question is related to the speed of sound in mediums of different densities. Generally it is said that sound travels faster in solids, than liquids than gases. It means that sound travels faster in denser medium than in lighter medium. Contrary to this, the details in physics also mention that the speed of sound increases with temperature. As at higher altitudes, where the temperature is lower (air is cooler), the speed of sound is less than that at the sea level.  In physics, the above argument/fact is explained as that due to the increase of temperature, the density of medium decreases and the medium particles offer less resistance to the propagation of sound waves, so its speed increases. I think that because of the nature of sound waves to be a mechanical wave, it needs a medium to travel and depends on the particle-to-particle contact, so in solid this particle-to-particle contact is more effective than in liquids than in gases, therefore the speed shall be high in denser medium and not in lighter mediums. Now if the temperature increases then density decreases and as explained above in physics, accordingly speed increases. I think these are two totally different explanations on the same aspect of speed of sound (speed depending on medium and their densities and temperature relation ) which are in contradiction to each other. My observations or interpretation of the above explanation may be wrong. Please advise me through your valuable expertise. Regards

Well, the speed of sound in gases is a different story than in solids.  http://hyperphysics.phy-astr.gsu.edu/hbase/sound/souspe3.html#c1  If you're determining the speed of sound in gas media, you have to determine how often the molecules collide.  This increases with temperature, of course. In solids, any disturbance of one atom is linked to forces directly applied to its neighbors.  That doesn't depend on the collision rate.  The two situations are quite different.

Physics

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#### Dr. Stephen O. Nelson

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I can answer most basic physics questions, physics questions about science fiction and everyday observations of physics, etc. I'm also usually good for science fair advice (I'm the regional science fair director). I do not answer homework problems. I will occasionally point out where a homework solution went wrong, though. I'm usually good at explaining odd observations that seem counterintuitive, energy science, nuclear physics, nuclear astrophysics, and alternative theories of physics are my specialties.

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Ph. D. from Duke University in physics, research in nuclear astrophysics reactions, gamma-ray astronomy technology, and advanced nuclear reactors.