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Help calculating decibel level from intensity of sound

  • #1

Homework Statement



Determine the decibel rating of the following intensities of sound.

I = 1.0 x 10-5 W/m2

Homework Equations



The equation which relates the intensity of a sound wave to its decibel level is:

dB = 10 * log( I / 1.0 x 10-12 W/m2)

The Attempt at a Solution



dB = 10 * log( 1 x 10-5 W/m2 / 1.0 x 10-12 W/m2) = ?

I put it into my calculator and can't actually get an answer out of it. I know the answer is 70dB as I looked in the answer booklet but I couldn't get that answer by entering the equation into it?

Any help would be greatly appreciated. Thanks
 

Answers and Replies

  • #2
Doug Huffman
Gold Member
804
110
It's right there, 10(12 - 5)=70 by inspection.
 
  • #3
It's right there, 10(12 - 5)=70 by inspection.
Thankyou. How would this one be worked out? I am very new to physics so equations are confusing at the moment:

dB = 10 * log( 6.1 x 10-6 W/m2 / 1.0 x 10-12 W/m2) = 68 dB

How would that be inputted into a calculator?

Thank you very much :)
 
  • #4
Doug Huffman
Gold Member
804
110
LOL Sorry, I haven't used a calculator in many years.

My collection of calculators (HP-35, 41, 48) live in the same box with a half-dozen slide rules.
 
  • #5
LOL Sorry, I haven't used a calculator in many years.
No worries. Thank you for your help!
 

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