Find Pressure amplitude from given decibels

  • #1

Homework Statement


A sound wave has an intensity level of 49 dB. What is the pressure amplitude of this wave?

Po= 2x10^-5

Homework Equations



β=10log(I/I0)
I≈P^2

The Attempt at a Solution


I can't figure out why I'm getting this problem wrong. So I set it up, 49=10log(I/I0)
-> 4.9=log(I/I0) -> 10^4.9=(I/I0) From there, I replaced the intensity for pressure amp (equation 2) -> p=(2*10^-5)√(10^4.9)
Pamp=.0056Pa

??
 

Answers and Replies

  • #2
I like Serena
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Hi Angie_Agnes! :smile:

You calculation looks good.
Any reason to doubt your result?
 
  • #3
yes, it's online homework and says it's wrong :(
 
  • #4
I like Serena
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Well, I think you have to tweak your result a bit then.
I believe it is numerically correct, but these online homework sites can be a bit difficult with the exact phrasing.
Btw, I'm assuming you did not make a typo in the problem statement...
 
  • #5
I copied and pasted the question, so no typo.... I typed it in as .005 Pa and .006Pa and both came up wrong. Frustrating!
 
  • #6
I like Serena
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With 2 significant digits in 49 dB, it should be 0.0056 Pa or 5.6 mPa.
I can't make anything else from it.
 
  • #7
THANK YOU! got it right as .0056Pa. Awesome!
 
  • #8
I like Serena
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Huh? But that is your original answer from your opening post! :confused:
 
  • #9
I looked back at my past answers, I had entered it .005 and .006 at first, before entering it finally as .0056.
 
  • #10
I like Serena
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All is well that ends well! :wink:
 

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