What Is the Speed of Sound and Vibration in Solids?

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    Solids Sound Vibration
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Discussion Overview

The discussion revolves around the comparison of the arrival times of mechanical impacts and sound waves in different media, specifically in the context of a pipeline and the propagation of sound in solids versus air. Participants explore the speeds of sound in various materials and the nature of mechanical waves.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants propose that sound travels faster in solids than in air, citing speeds of approximately 5000 m/s in steel compared to 330 m/s in air.
  • Others argue that the arrival times of mechanical impacts and sound waves should not be assumed to be different, questioning the basis for such an assumption.
  • A participant introduces a scenario involving a fish and a droplet, asking which would reach the fish first: sound or the surface wave, suggesting that sound in water is typically faster than surface waves.
  • Some responses highlight that sound energy in a confined medium, like a pipe, experiences less attenuation compared to sound traveling through air.
  • There is a discussion about the definitions of "mechanical impact" and "sound of impact," with suggestions that the interpretation of these terms may influence the understanding of the problem.
  • Participants note that seismic waves in solids travel at much higher speeds than sound in air, emphasizing the relative speeds of different types of waves in various media.
  • One participant mentions that tsunami waves have different mechanisms and speeds, which can vary significantly based on ocean depth.

Areas of Agreement / Disagreement

Participants express differing views on the arrival times of mechanical impacts versus sound waves, with no clear consensus reached. Some agree on the general principle that sound travels faster in solids, while others question the assumptions underlying the discussion.

Contextual Notes

Participants reference various speeds of sound and mechanical waves, but there are unresolved aspects regarding the definitions of terms and the specific conditions under which these comparisons hold true.

Ronie Bayron
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Say, I have 10 Km (1m dia.) exposed pipeline under construction phase. 9 Km of the pipe line was already done. Its so happen that at the next pipe length installation, the plane operator mishandled the pipe and it collided at the end where connection should be made, big time that the magnitude of the force would enough to make impact on mountings, support braces of the pipe.

Which would you think arrive first at the other end? Is it the mechanical impact or the sound of impact?
 
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Why assume arrival times are different?
 
Hi and welcome.
It would be the speed of sound in the two media that counts here. Sound in air travels at about 330m/s and 5000m/s in steel. Put your ear to the pipe and you would hear that long before the sound of the crash got to you. Also, because the sound energy in the pipe wall does not spread out, as it does in air, the sound would be less attenuated. At 9km, the sound would hardly get to you, via the air, except on a very quite night.
Remember the cowboy films in which the outlaws stick their ears on the railroad track to detect an oncoming train? Well, it made sense - unlike a lot of other Hollywood notions.
 
You're asking does sound travel through solids faster than its speed through air.
 
Dr. Courtney said:
Why assume arrival times are different?

Hi, to you sir thank you for the response. I am intrigue on the fact, that there is a little confusions I got from the fundamentals I learned about sound and mechanical vibration.
water-droplet-585x298.jpg
say I am a fish(sensitive to sound) which is 5m away from the droplet. Which will reach me first (the sound or the first wave that travels along the surface?
 
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sophiecentaur said:
Hi and welcome.
It would be the speed of sound in the two media that counts here. Sound in air travels at about 330m/s and 5000m/s in steel. Put your ear to the pipe and you would hear that long before the sound of the crash got to you. Also, because the sound energy in the pipe wall does not spread out, as it does in air, the sound would be less attenuated. At 9km, the sound would hardly get to you, via the air, except on a very quite night.
Remember the cowboy films in which the outlaws stick their ears on the railroad track to detect an oncoming train? Well, it made sense - unlike a lot of other Hollywood notions.
Yes thank you, i know.
 
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Ronie Bayron said:
say I am a fish(sensitive to sound) which is 5m away from the droplet. Which will reach me first (the sound or the first wave that travels along the surface?

The speed of sound in water is usually much much faster than a surface wave. However some tsunami waves do travel very fast.
 
sophiecentaur said:
. Put your ear to the pipe and you would hear that long before the sound of the crash got to you. Also, because the sound energy in the pipe wall does not spread out, as it does in air, the sound would be less attenuated. At 9km, the sound would hardly get to you, via the air, except on a very quite night.

or a variation on that ...
consider the sound wave that is traveling in the air, within the pipe
It is well confined like a wave guide. there's going to be a lot less attenuation of that sound wave ( compared to the free air one)
but, yes, the metallic clang is still going to arrive firstDave
 
davenn said:
or a variation on that ...
consider the sound wave that is traveling in the air, within the pipe
It is well confined like a wave guide. there's going to be a lot less attenuation of that sound wave ( compared to the free air one)
Quiz Question -- What does the clang sound like when it arrives at the far end?

(It helps if you've ever been to the Exploratorium in San Francisco, and clapped your hands at the base of the long reflecting tube...) :smile:

http://www.exploratorium.edu/explore

EDIT
http://exs.exploratorium.edu/exhibits/echo-tube/
 
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  • #10
Ronie Bayron said:
the sound or the first wave that travels along the surface
That picture is of a surface wave. That is not how a fish will hear sound through the water, which is a compression wave in the body of the water. Surface waves, as we have all seen, travel at (depending on the wavelength) between mm/s and a few m/s. The speed of compression waves is much higher (as stated earlier) than sound (also compression) waves in air.
 
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  • #11
Ronie Bayron said:
Which would you think arrive first at the other end? Is it the mechanical impact or the sound of impact?

The answer might depend on the definition of "mechanical impact" vs "sound of impact".

If we graph the x (horizontal) position of the non-impacted end of the pipe vs time, what would the graph look like? Would it have an initial interval where it just oscillated? Or would the initial interval be a steady increase or decrease before we saw any oscillation superimposed on the shape of the graph?
 
  • #12
Stephen Tashi said:
The answer might depend on the definition of "mechanical impact" vs "sound of impact".

If we graph the x (horizontal) position of the non-impacted end of the pipe vs time, what would the graph look like? Would it have an initial interval where it just oscillated? Or would the initial interval be a steady increase or decrease before we saw any oscillation superimposed on the shape of the graph?
Thank you, Stephen Tashi. I get it now.

It would take a minimal effort to be heard, other than carrying the whole baggage of clothes of my wife at the airport:smile:. (A parallel) So, sound travels fast than the ,mechanical wave on the surface.
 
  • #13
Ronie Bayron said:
So, sound travels fast than the ,mechanical wave on the surface.

on the surface of what ?

did you not read the other responses ?

mechanical wave within the metal of the pipe is always going to be faster than the sound wave in the air
the same for water or any other liquid or solid relative to air/ other gas

seismic waves in the "solid' Earth travel at around 8km / sec ... they are a mechanical wave
In dry air at 20 °C, the speed of sound is 343.2 metres / sec very much slower

Tsunami waves in the open ocean are a bit of a different mechanism and they have a speed of around 800 km / hr ( varies with ocean depth)Dave
 
  • #14
davenn said:
on the surface of what ?

did you not read the other responses ?

mechanical wave within the metal of the pipe is always going to be faster than the sound wave in the air
the same for water or any other liquid or solid relative to air/ other gas

seismic waves in the "solid' Earth travel at around 8km / sec ... they are a mechanical wave
In dry air at 20 °C, the speed of sound is 343.2 metres / sec very much slower

Tsunami waves in the open ocean are a bit of a different mechanism and they have a speed of around 800 km / hr ( varies with ocean depth)Dave
Yes, thank you Davenn. I am settled for my answer for the moment. I might cross the other side so soon enough that things will become a bit more complicated for me to solve.
 
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  • #15
davenn said:
Tsunami waves in the open ocean are a bit of a different mechanism and they have a speed of around 800 km / hr
This is true but the wave speed of a surface water wave is wavelength dependent. The speed can, as I stated earlier, be just a few mm per second. The surface wave speed could never exceed the bulk pressure wave speed (P waves).
 
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