Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Sound and Vibration in Solids

  1. Nov 4, 2015 #1
    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?
     
  2. jcsd
  3. Nov 4, 2015 #2
    Why assume arrival times are different?
     
  4. Nov 4, 2015 #3

    sophiecentaur

    User Avatar
    Science Advisor
    Gold Member

    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.
     
  5. Nov 4, 2015 #4

    NascentOxygen

    User Avatar

    Staff: Mentor

    You're asking does sound travel through solids faster than its speed through air.
     
  6. Nov 5, 2015 #5
    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?
     
    Last edited: Nov 5, 2015
  7. Nov 5, 2015 #6
    Yes thank you, i know.
     
    Last edited: Nov 5, 2015
  8. Nov 5, 2015 #7

    CWatters

    User Avatar
    Science Advisor
    Homework Helper

    The speed of sound in water is usually much much faster than a surface wave. However some tsunami waves do travel very fast.
     
  9. Nov 5, 2015 #8

    davenn

    User Avatar
    Science Advisor
    Gold Member

    or a variation on that .....
    consider the sound wave that is travelling 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 first


    Dave
     
  10. Nov 5, 2015 #9

    berkeman

    User Avatar

    Staff: Mentor

    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
     
  11. Nov 5, 2015 #10

    sophiecentaur

    User Avatar
    Science Advisor
    Gold Member

    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.
     
  12. Nov 5, 2015 #11

    Stephen Tashi

    User Avatar
    Science Advisor

    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?
     
  13. Nov 5, 2015 #12
    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.
     
  14. Nov 5, 2015 #13

    davenn

    User Avatar
    Science Advisor
    Gold Member

    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
     
  15. Nov 5, 2015 #14
    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.
     
    Last edited: Nov 5, 2015
  16. Nov 6, 2015 #15

    sophiecentaur

    User Avatar
    Science Advisor
    Gold Member

    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).
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Sound and Vibration in Solids
  1. Sound waves in solids? (Replies: 1)

  2. Why is Sound produced (Replies: 11)

Loading...