# The Naked Scientists Forum

### Author Topic: What is the maximum speed of sound?  (Read 14936 times)

#### imd321

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##### What is the maximum speed of sound?
« on: 04/06/2009 12:03:35 »
Is there a theoretical maximum speed of sound?
« Last Edit: 04/06/2009 17:37:12 by chris »

#### lyner

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##### Re: What is the maximum speed of sound?
« Reply #1 on: 04/06/2009 12:22:57 »
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
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.

#### Don_1

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##### Re: What is the maximum speed of sound?
« Reply #2 on: 04/06/2009 14:01:08 »

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!

#### lightarrow

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##### Re: What is the maximum speed of sound?
« Reply #3 on: 04/06/2009 15:43:54 »
Is there a theoretical maximum speed of sound?
c.

#### DoctorBeaver

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##### What is the maximum speed of sound?
« Reply #4 on: 04/06/2009 19:15:20 »
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?

#### lyner

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##### What is the maximum speed of sound?
« Reply #5 on: 04/06/2009 21:37:36 »
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.

#### LeeE

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##### What is the maximum speed of sound?
« Reply #6 on: 05/06/2009 16:53:01 »
Does anyone have any idea what the speed of sound would be for a Carbon nanotube?

#### lyner

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##### What is the maximum speed of sound?
« Reply #7 on: 05/06/2009 19:10:09 »
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.

#### imd321

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##### What is the maximum speed of sound?
« Reply #8 on: 06/06/2009 09:47:49 »
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?

#### Chemistry4me

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##### What is the maximum speed of sound?
« Reply #9 on: 06/06/2009 12:45:56 »

#### lyner

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##### What is the maximum speed of sound?
« Reply #10 on: 06/06/2009 21:02:46 »
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).

#### Raghavendra

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##### What is the maximum speed of sound?
« Reply #11 on: 08/06/2009 09:27:37 »
c=( Speed of light)

#### Yomi

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##### What is the maximum speed of sound?
« Reply #12 on: 08/06/2009 09:29:19 »
Can "C" be maximum speed of sound

#### Raghavendra

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##### What is the maximum speed of sound?
« Reply #13 on: 08/06/2009 09:36:10 »
depends upon direction.... applying doppler effect

#### Yomi

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##### What is the maximum speed of sound?
« Reply #14 on: 08/06/2009 09:39:52 »
However it cannot reach value of "c" under any circumstances so u cannot make doppler's theory on this account ......

#### Raghavendra

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##### What is the maximum speed of sound?
« Reply #15 on: 08/06/2009 10:51:53 »
however some law is applicable

#### lyner

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##### What is the maximum speed of sound?
« Reply #16 on: 08/06/2009 11:08:47 »
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.
« Last Edit: 08/06/2009 11:10:32 by sophiecentaur »

#### LeeE

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##### What is the maximum speed of sound?
« Reply #17 on: 08/06/2009 20:15:28 »
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.

#### erickejah

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##### What is the maximum speed of sound?
« Reply #18 on: 08/06/2009 21:08:43 »
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.

#### lyner

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##### What is the maximum speed of sound?
« Reply #19 on: 08/06/2009 21:33:24 »
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.

#### erickejah

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##### What is the maximum speed of sound?
« Reply #20 on: 08/06/2009 22:14:50 »
what about d (speed of darkness)

#### LeeE

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##### What is the maximum speed of sound?
« Reply #21 on: 09/06/2009 21:26:44 »
what about d (speed of darkness)

Let's not start running backwards before we've learned to walk forwards

#### lightarrow

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##### What is the maximum speed of sound?
« Reply #22 on: 09/06/2009 21:38:35 »
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...

#### erickejah

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##### What is the maximum speed of sound?
« Reply #23 on: 10/06/2009 01:27:25 »
o well never mind. I wish I could have mentors like you in real life.

#### lightarrow

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##### What is the maximum speed of sound?
« Reply #24 on: 10/06/2009 15:36:35 »
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.......

#### The Naked Scientists Forum

##### What is the maximum speed of sound?
« Reply #24 on: 10/06/2009 15:36:35 »