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Sound waves and gravity question

  1. Jun 27, 2003 #1
    [SOLVED] Sound waves and gravity question

    Just a small question: are sound waves affected by gravity, and can thye have an initial and final velocity, or do they always have a constant velocity and do not need to accelerate?
     
  2. jcsd
  3. Jun 28, 2003 #2

    HallsofIvy

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    Sound waves are compression waves in the atmosphere (or water, metal, etc. if they are moving through those).

    Since they have neither mass nor the concentrated energy of light, they are not affected by gravity in the sense of being "bent" by gravity.

    The speed of a sound wave is dependent on the "natural frequency" of the medium and so is affected by such things as air density. It is possible for sound to "reflect" or "diffract" when moving from an air mass of one density to another.
     
  4. Jun 28, 2003 #3
    Sound waves are inside movement of medium. If sound waves are affected by gravity, it would come from the effect of gravity on the medium. Speed and acceleration of sound waves are to come from property of the medium such as elasticity, temperature, anisotropy, existence of defects, etc.
     
  5. Jun 28, 2003 #4
    Hmm, so if I'm neglecting air resistance, then I don't have to worry about the sound "reflecting" or "diffracting"?

    I suppose I should explain the problem that I'm deriving this question from ^^;;

    Basically, it asks you how far sound has traveled in 3.4 seconds if there is no air resistance. So I'm assuming, by your replies, that with no air in the way, sound would have a constant velocity and I wouldn't need to factor in its acceleration?

    Sorry if this all seems rudimentary to you, I'm starting AP Physics the coming school year, so I'm only going over pretty much the basics =P
     
  6. Jun 28, 2003 #5
    No air, no sound, isn't it. Sound we hear is usually a vibration of air.
     
  7. Jun 28, 2003 #6
    Well, I never said these problems made sense :P
     
  8. Jun 28, 2003 #7
    Air resistance doesn't apply to sound waves. Its not like a plane. Sound needs a medium to travel through. Without air (or other medium) there can be no sound. True, sound loses energy as it vibrates through the air, but that can't be considered air resistence in the most familiar sense of the word. If you negelect that, the sound wave will travel forever, unless it hits something else, that is.
     
  9. Jun 29, 2003 #8
    Or maybe leave the medium to space too ?
     
  10. Jun 29, 2003 #9
    Actually, there are waves in the upper atmosphere which are largely governed by gravity. Have you ever observed 'rippled clouds'? Well, I think these are created by 'orographic motion' in the atmosphere, where the gravitational component gets in the same order of magnitude as adiabatic pressure & density. I learned this under the German term of 'Atmosphärische Schwerewellen'. Well I guess you can't really call this 'sound'. But you get the solution from the same wave equation, if you *don't* neglect gravity.
     
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