1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Intensity and dB level

  1. Apr 29, 2015 #1
    1. The problem statement, all variables and given/known data
    The intensity of a certain spherical wave is 8.0 W/m^2 at a distance of 1.0 m from the source. If the medium is isotropic and nonabsorbing, calculate the decibel intensity 100m from the source.

    2. Relevant equations
    β=10ln(I1/I0)

    3. The attempt at a solution
    I know how to use these equations... And to find the original dB level i use
    β=(10dB)ln(8.0/10^-12)

    Im just not sure what to do to find intensity 100m away?
     
  2. jcsd
  3. Apr 29, 2015 #2

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    What do you mean with "original dB level"?

    How does intensity depend on distance for spherical waves without absorption?
     
  4. Apr 29, 2015 #3

    haruspex

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    2016 Award

    "Decibel" is very confusing because the term is used both for relative and absolute intensities. As far as I am aware, the unit dB always denotes (or should always denote) a relative intensity. If an absolute intensity is intended then it should be qualified to indicate the reference level, like dBm or dBmW.
    Where does your 10-12 come from?
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: Intensity and dB level
  1. Intensity levels (Replies: 1)

Loading...