What is the fastest substance for sound to travel in?

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Discussion Overview

The discussion centers on identifying the substance in which sound travels the fastest. Participants explore various materials, including solids and potential exotic states of matter, while considering factors such as density, elasticity, and temperature. The conversation includes both theoretical and practical aspects of sound propagation.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant notes that sound travels faster in denser media, particularly in solids, and suggests that iridium or solid hydrogen might be candidates for the fastest sound travel.
  • Another participant proposes that diamond likely has the fastest speed of sound due to its high stiffness and low density.
  • A different participant mentions that the speed of sound in solids can be calculated using the formula involving Young's modulus and Poisson's ratio, indicating that elasticity plays a significant role.
  • There is a suggestion that sound might travel faster in an Einstein-Bose condensate, though this is not elaborated upon.
  • One participant questions whether the frequency of sound affects its speed, leading to a discussion about sound wavelengths and atomic distances in solids.
  • Another participant provides a rough estimate of the speed of sound in a typical solid and discusses how it might change at certain frequencies.
  • It is mentioned that factors such as temperature, pressure, and molecular weight also influence the speed of sound in different materials.

Areas of Agreement / Disagreement

Participants express multiple competing views regarding which substance allows for the fastest sound travel, with no consensus reached on a definitive answer. There is also uncertainty about the impact of frequency on sound speed.

Contextual Notes

Some participants reference specific formulas and properties of materials, but there are limitations in the discussion regarding the exact conditions under which these properties apply, as well as the need for further clarification on the effects of frequency.

alexandrae
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**this is not a homework question**

I need to know in which substance does sound travel fastest in. I know that sound travels faster when the medium is denser, therefore solids, however I would like to go more in depth. I've heard that it is iridium or hydrogen solid, but I can't get a definite answer. I was wondering if anybody knew for sure?

much appreciated!
 
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In solids speed of sound = sqrt ( E / 3*density*( 1-2v) )

E is Young's modulus (the stiffness)
v is Possion ratio (a measure of how much the material expands sideways when you press it)

At a guess the fastest speed of sound would probably be in diamond - it's hard = stiff
 
mgb_phys said:
In solids speed of sound = sqrt ( E / 3*density*( 1-2v) )

E is Young's modulus (the stiffness)
v is Possion ratio (a measure of how much the material expands sideways when you press it)

At a guess the fastest speed of sound would probably be in diamond - it's hard = stiff

Speed of sound should be same as the propagation speed of a mechanical vibration in the medium, right?
 
would sound travel faster in an Einstein-Bose condensate.
 
jobyts said:
Speed of sound should be same as the propagation speed of a mechanical vibration in the medium, right?

Yes, remember that sound IS just a mechanical vibration (which happens to be in the audible range) so from a physical point of view there is no difference between the two.
 
hey I'm in eighth grade, can you give me some examples? How would I use the formulas you gave me to find out the answer? Is it a natural or manmade substance?
 
mgb_phys said:
At a guess the fastest speed of sound would probably be in diamond - it's hard = stiff

Diamond also has a low density (3.5 g/cc), which helps.
 
elasticity increases the speed of sound. so metals will give highest speed of sound in them. not only this the temperature, pressure, density, and molecular wt. also play role.
 
  • #10
Does the frequency of the sound matter?
 
  • #11
jobyts said:
Does the frequency of the sound matter?

In the human range of audible sound, no.

However, what I remember from my solid state physics (taken 25-30 years ago), at frequencies where the sound wavelength is comparable to the distance between adjacent atoms the speed of sound does change.

I don't remember at what frequencies this typically happens, or whether the speed of sound becomes faster or slower ... perhaps somebody else knows?

To get a ballpark estimate, figure a speed-of-sound of 5000 m/s in a "typical" solid, and a wavelength of 0.2 nm:

f = v/λ = 5x103 / 2x10-10 Hz ~ 2x1013 Hz​

I.e., at frequencies corresponding to I.R. radiation we'd expect changes in the speed of sound.

FYI, I found this listing for speed of sound in some different materials. Berylium is 12.9 km/s, slightly higher than diamond (12 km/s)
http://hypertextbook.com/physics/waves/sound/
 
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