Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: imd321 on 04/06/2009 12:03:35
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Is there a theoretical maximum speed of sound?
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Do you mean is there a limit to the speed of sound in any substance or just in air?
It is much higher in solids where its value is given by
Square root of (modulus/ density)
The Modulus is, essentially, the stiffness.
In steel, this comes out at about 15 times higher than the speed of sound in air.
A very stiff, light material would have the highest speed of sound - possibly something like Diamond?
http://hyperphysics.phy-astr.gsu.edu/Hbase/Tables/soundv.html (http://hyperphysics.phy-astr.gsu.edu/Hbase/Tables/soundv.html)
That link confirms my notion but there may be some other crystal, perhaps, with a higher speed. But there would be a limit, simply due to availability of a suitable substance.
The sound in a gas is 'carried' by the moving molecules bumping into each other and it will increase as the temperature increases - because they take less time between collisions. At very high temperatures the gas would become a plasma but I guess the speed would still be higher without limit. Shock waves / sound would travel very quickly inside a star, I imagine.
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It is much higher in solids
This is borne out by the speed at which the taxpayers voice enters one ear of a politician and exits the other!
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Is there a theoretical maximum speed of sound?
c.
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The sound in a gas is 'carried' by the moving molecules bumping into each other and it will increase as the temperature increases - because they take less time between collisions.
The hotter the gas, the fewer molecules there are in a given volume. Doesn't it follow, therefore, that they would have further to travel?
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The number of molecules in a given volume doesn't really make any difference.
When the molecules collide, they exchange momentum, so there may be more collisions in a second but the speed of sound depends mainly on how long it takes to transmit pressure. This relates to the time between collisions divided by the number of collisions. i.e. it's the temperature (speed of molecules (that makes most difference.
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Does anyone have any idea what the speed of sound would be for a Carbon nanotube?
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They are very short - so, to discuss sound transmission, you'd be talking very high frequencies. There are quite a few links about the transmission of thermal energy through nanotubes by phonons. I guess that would be some sort of an answer or at least a pointer in the right direction.
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Thanks, my question was about what is the maximum speed that sound could travel in any environment. For example are there any circumstances real or theoretical where sound could travel at the speed of light?
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Is there a theoretical maximum speed of sound?
c.
http://www.thenakedscientists.com/forum/index.php?topic=23408.msg255943#msg255943
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The speed at which sound (mechanical vibrations) is propagated relates to the speed at which the particles can move. The limit to the speed at which a particle will move depends upon the force acting on it and the time the force is applied. For a vibrating particle, the forces are constantly changing direction so the particle can never get 'very' fast. Bearing in mind how hard it is to accelerate a particle to anything like light speeds in an accelerator - given as much time as you want - it's not surprising that the maximum speed a particle can achieve, whilst vibrating, is always a lot lower than c. Hence, the speed of sound in any substance must be a lot less than c. It's just over one millionth c in air so you can be a thousand times faster and still be nowhere near.
There is also the issue that the average speed goes up with temperature. Any solid will vaporise at high temperature so you are then dealing with a gas (except, I suppose, under very high pressure).
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c=( Speed of light)
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Can "C" be maximum speed of sound
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depends upon direction.... applying doppler effect
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However it cannot reach value of "c" under any circumstances so u cannot make doppler's theory on this account ......
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however some law is applicable
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Can "C" be maximum speed of sound
Was that an upper case "C", deliberately. The lower case c normally refers to the speed of light in vacuo.
"Some law" eh? The law of diminishing returns, I suspect.
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The speed of sound cannot reach 'c' because the speed of sound depends of the movement of matter, and no matter can move at 'c' because it would require infinite energy.
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V=λf
V=velocity
λ=Wavelength
f=Frequency
since it depends in the material in which the sound wave vibrates we will never know. Until we have found and tested each material of the universe.
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Not necessarily. There are upper and lower limits to the parameters involved. We've found all the elements and there are limits to structures and densities. The speed of energy flow inside a star is very slow - afaik, the energy flow is by photons - not by phonons (vibrations) so the effective speed of sound in a star must be very low.
Outside a star we won't find any substance which could fulfill the requirements and it can't be inside a star.
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what about d (speed of darkness)
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what about d (speed of darkness)
Let's not start running backwards before we've learned to walk forwards [;)]
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what about d (speed of darkness)
It is certainly greather than c. You can send a light pulse where you want, but darkness is already there... [;)]
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[:D] o well never mind. I wish I could have mentors like you in real life. [:)]
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Not necessarily. There are upper and lower limits to the parameters involved. We've found all the elements and there are limits to structures and densities. The speed of energy flow inside a star is very slow - afaik, the energy flow is by photons - not by phonons (vibrations) so the effective speed of sound in a star must be very low.
Outside a star we won't find any substance which could fulfill the requirements and it can't be inside a star.
Your post made me wonder about what could be the speed of sound in a neutron star, or in a quark star, or in a gluon star.......
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I suppose the forces involved would be nuclear forces so would the effective modulus be enormous enough to make up for the increased density? (Treating the problem classically - which is always a good start) There wouldn't be any photons in there, would there? Or would we still find gamma rays?