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Sound wave energy transfer to heat water?

  1. Sep 28, 2008 #1
    I was just wondering if anyone has any idea on how I would go about working this out. I have performed the experiments at home, placing a container of water on top of a speaker and then playing a high frequency and high dB sound through them, however, I can not find any equations online or in my college text books which describe the calculations required to find the energy given off in a sound wave.

    In a nutshell, I'm specifically after some sort of equation which describes the relationship between sound waves and heat transfer.

    Any help appreciated :)

  2. jcsd
  3. Sep 28, 2008 #2


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    Good luck.

    This is why people spend yrs getting degrees in Physics or Engineering. To solve such a problem you need to apply the basic principles and derive the relationships involved.

    For your case there is NO way go come up with, from first principles the fraction of sound energy which enters the water and causes a heat gain.

    It is trivial to compute the energy required to increase the temperature of a known mass of water a known amount. Measure your temperature increase, compute the energy put in. Then measure the amount of energy produced by your amp. The difference will be the amount of energy lost to the surroundings.
  4. Sep 28, 2008 #3
    Sorry, I wasn't actually asking for someone to create a formula for me, but rather, point me in the direction to where someone may have performed the same experiment and done the maths already.

    There is a way of doing it as there is a fact I've found on the internet before that says:

    "If you yelled for 8 years, 7 months and 6 days you would have produced enough sound energy to heat one cup of coffee."

    I can't find anything further on that fact though :(
  5. Sep 28, 2008 #4


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    It should not be difficult to find something about the energy content of a sound wave. But, as I said above that does NOT tell you how much of that energy is transferred to your water container. There is not going to be a canned equation which tells you that. Your best bet is experimental. IE measure it.
  6. Sep 28, 2008 #5


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    Look up "high intensity focused ultrasound". That may have some useful information although it is dealing exclusively with frequencies above the audio range.
  7. Sep 28, 2008 #6


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    That alone is enough for a preliminary calculation.

    Even if you had a speaker's volume turned up to 10 times the power of a person yelling, it would still take nearly a year (10 months) to heat a cup of coffee.

    And it goes without saying, that cup would have to be extremely well insulated! Yes, insulated well enough that it would not lose any appreciable heat in 10 months. I don't know of any insulation that is that good.

    Sounds like an impossible task.
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