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Decibels, pressure & displacement amplitudes

  1. Aug 7, 2007 #1
    1. The problem statement, all variables and given/known data
    A jackhammer emits sound at a decibel level of 130 dB. The wavelength of the sound is 1.0 m. What is the linear sound intensity? What is the pressure amplitude? What is the displacement amplitude?

    2. Relevant equations
    Beta = 10 log (I / Io)

    3. The attempt at a solution
    Solved for question 1, the linear sound intensity, and received an answer of 10 Watts/meter. I combed my physics text and have not found an equation that wil provide me with either the pressure or displacement amplitude based upon the information I am given. I found a lengthy equation using density, angular velocity, and some variable "s naught" among other variables, and I simply don't have this information or have little means of finding it. Could someone please just help me find the right equations??????? Thank you!
  2. jcsd
  3. Aug 7, 2007 #2


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    I think that lengthy equation is what you need. It should involve speed of sound, density of air, frequency or wavelength of the sound... The speed of sound and density of air should be given as constants in your text.
  4. Aug 8, 2007 #3
    Okay, I think I figured out what the pressure amplitude is...but what about the displacement amplitude? Again, I have no means (as far as I can see) of calculating omega or frequency or other factors needed to solve for the amplitude....

    Please help! :)
  5. Aug 8, 2007 #4


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    Frequency of a soundwave is just speed of sound divided by wavelength... what other terms do you need?
  6. Aug 8, 2007 #5
    I was actually able to finally figure it out. Thanks for the help!
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