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Can you break the sound barrier under water?

  1. Aug 21, 2009 #1
    Has it be done? And whats the sound barrier in space and can it be broken?
     
  2. jcsd
  3. Aug 21, 2009 #2

    negitron

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    There is no sound barrier in space.

    In fresh water at 20 C, the speed of sound is ~1482 m/s; tough to beat in a medium that's about 1000 times as dense as air.
     
  4. Aug 21, 2009 #3

    jambaugh

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    Certainly a normal sized object can in principle pass through a body of water faster than the speed of sound in the water. But in so doing I don't think you can say its "in water" anymore as the objects passage would create a large cavitation and vaporize the surrounding water.

    An example I would imagine is substantial sized meteor hitting the ocean. Likely you have cases of the meteor drilling though to the ocean floor faster than conventional sound would travel from surface to floor.

    But again I wouldn't call it breaking the sound barrier in water so much as breaking the water itself. The big difference is that water is effectively incompressible while air is compressible. This means the speed of sound in water is very very high. The expansion/compression happening on both sides of the shock wave formed by an object in the air would not necessarily change the phase. This can't really happen with water. The shock-wave formed would be a boundary between water and very high pressure steam.

    I would add to negatron's comment ...
    remember "In space, noone can hear you scream!"
     
  5. Aug 21, 2009 #4
    no sound barrier in space? so if i yell in another galaxy earth would hear it instantly?
     
  6. Aug 21, 2009 #5
    In space no one can hear you scream.Sound needs a medium(solid liquid or gas) to travel through.No medium no sound.
     
  7. Aug 21, 2009 #6
    aha... thats weird. so how would you go about hearing what the sun sounds like?
     
  8. Aug 21, 2009 #7

    Danger

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    I would have to have a military expert such as Russ or Andre to verify this, but I'm pretty sure that both the US and the Russians developed supersonic torpedoes. They are essentially underwater rockets.
    It seems to me that at least one of the designs vented pressurized air from the nose in order to form a bubble around itself and thus minimize water resistance.
     
  9. Aug 21, 2009 #8

    Danger

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    You get a fire-proof microphone and stick into the sun to a depth where the gas/plasma density is high enough to conduct sound.
    You will need a really long cable, and it will deafen you.
     
  10. Aug 21, 2009 #9
    I've just gotta ask - of what material will said microphone and cable be constructed? In order to avoid being vaporized, will you install the device at night?
     
  11. Aug 21, 2009 #10
    Is it just me, or does this question smell funny?
     
  12. Aug 21, 2009 #11
    trolling a bit but i am curious what a nuclear fusion sounds like.
     
  13. Aug 21, 2009 #12
    Maybe I needed to say a bit more so it didn't come off that way.

    Emergent phenomena only make sense in the domain which they apply. Billiard balls don't exert pressure along the surface of a pool table. A hydrogen atom doesn't have a temperature. And you can't have sound without having something to propagate it. Oh. And sentences don't have odors ;-)
     
  14. Aug 21, 2009 #13

    Danger

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    Of course.
    I was thinking of a rubber cable in a braided silk sheath. The microphone housing would, naturally, have to be composed of Silly Putty.
     
  15. Aug 21, 2009 #14
    Well this thread made me laugh!
     
  16. Aug 21, 2009 #15

    Danger

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    Jeez, but you are easily amused... :biggrin:
     
  17. Aug 21, 2009 #16

    russ_watters

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    Rocket propelled torpedos yes, supersonic no. IIRC, they go a couple hundred mph.
     
  18. Aug 21, 2009 #17

    mgb_phys

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    The russian Shkval super cavitating torpedeo can do 400km/h using a film of bubbles

    Particles (eg neutrinos) of course can go faster than light in water.
     
  19. Aug 21, 2009 #18

    Danger

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    Thanks, both Russ and Mgb for clarifying that. My memory is always a bit hazy.
     
  20. Aug 21, 2009 #19

    Borek

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    Could be Kursk sunk after Shkval torpedo accident.
     
  21. Aug 21, 2009 #20

    Danger

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    It was widely reported that it was a torpedo accident, but I don't recall hearing a model name or number associated with it. It's quite possible that it was a Shkval. A warhead is a warhead, though, regardless of the delivery system. It could just as easily have been a defective mine, or whatever else they carry. (I do have the armaments of almost all subs available, but I don't know exactly where the book is since I'm in the midst of moving.)
     
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