Speed of sound: viscosity dependece in liquids and solids

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SUMMARY

The speed of sound in liquids and solids is primarily influenced by factors such as bulk modulus (or Young's modulus for solids) and density, rather than viscosity. Viscosity is not a relevant factor for solids, and its impact on sound speed in liquids is not generally accepted in the scientific community. The discussion referenced a lack of direct equations relating viscosity to sound speed, highlighting that existing literature on this topic is outdated, with significant papers dating back 50-60 years. The consensus is that viscosity does not play a direct role in determining the speed of sound in either state of matter.

PREREQUISITES
  • Understanding of bulk modulus and Young's modulus
  • Knowledge of density and its role in wave propagation
  • Familiarity with sound wave mechanics in different media
  • Basic grasp of fluid dynamics and properties of liquids and solids
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  • Research the relationship between bulk modulus and sound speed in solids
  • Explore the effects of density on sound propagation in various materials
  • Investigate historical papers on sound speed in viscous liquids
  • Learn about the limitations of viscosity as a factor in sound speed calculations
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Physicists, acoustics researchers, and engineering professionals interested in the principles of sound propagation in different materials, particularly those studying the effects of material properties on sound speed.

phixmin
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Hello,

Wikipedia gave me prior hints as to how the speed of sound depends on viscosity but after searching on Google scholar and Google, I have yet to find any direct equations/findings that give a direct relationship of the speed of sound to the visocisty of fluids and solids outside of: http://iopscience.iop.org/article/10.1088/0370-1301/66/5/303/pdf

My question: does anyone know how the speed of sound depends on the viscosity of liquids and solids? Are there any known formulas?
 
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russ_watters said:
What article? From what I see, no form of the word "viscosity" appears in the wiki article on the speed of sound:
https://en.m.wikipedia.org/wiki/Speed_of_sound
I didn't state that it was from the speed of sound wiki.
 
mk9898 said:
Yep I already saw this post but it is only for liquids not for solids.

Huh? Viscosity is a term we use only for fluids, not solids.
 
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mk9898 said:
I didn't state that it was from the speed of sound wiki.
No, you didn't. So why don't you help us stop guessing and provide your source!

Further, the fact that it isn't in a relevant article should tell you something.
 
That linked PF thread is full of some extreme nonsense. Sound speed is not generally considered to have a direct relationship with viscosity.
 
Hm then what does the speed of sound depend on when the sound moves with longitudinal waves through solids?
 
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Most commonly the bulk modulus (Young's modulus, for a solid) and density. Viscosity isn't even a quantity that makes sense for a solid.
 
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  • #11
mk9898 said:
Hm then what does the speed of sound depend on when the sound moves with longitudinal waves through solids?
This is fully covered in the wiki I linked: elasticity(several ways to describe: "bulk modulus" or "young's modulus" for solids) and density.

Your posts in this thread are very odd. It seems like you want a certain answer and are ignoring answers you don't like and questions we ask you that would better help us understand your issue. Please put more effort into helping us help you.
 
  • #12
You are all totally right with the viscosity...don't know what I was thinking there. Just a mistake Russ ;).

So for liquids boneh3ad, since the other post has things that are nonsense in it, would you or anyone know if there is a direct formula with the viscosity being a part of determining the speed of sound? The comment by Lord J with the paper helps but I'm surprised that the only two papers that I now know of are 50-60 years old.

For solids, is there also a general formula for the speed of sound through solids?
 
  • #13
mk9898 said:
You are all totally right with the viscosity...don't know what I was thinking there. Just a mistake Russ ;).

So for liquids boneh3ad, since the other post has things that are nonsense in it, would you or anyone know if there is a direct formula with the viscosity being a part of determining the speed of sound? The comment by Lord J with the paper helps but I'm surprised that the only two papers that I now know of are 50-60 years old.

For solids, is there also a general formula for the speed of sound through solids?
The answer remains: no, viscosity is not a generally accepted factor in the speed of sound in liquids. And the linked wikipedia article still contains all the answers to your questions.

I'm going to lock the thread now since the questions have been fully answered and I don't want it to continue going around in circles. Thanks everyone.
 
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