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Homework Help: Amplitude of sound wave in by 50%

  1. Sep 26, 2008 #1
    Any kind soul to help me with this questions...i am stuck

    qn. The amplitude of vibration of a certain sound wave is increase by 50%. What is the corresponding increase in the decibel level of the sound?

    My attempt..

    beta= 10 log ( I/Io)

    lets just take I = 2.0 x 10^-7
    let just take Io= 1.00 x 10^-12

    then 10 log( 2.0 x 10^-7/1.00 x 10^-12) = 10 log (2.0 x 10^5) = 53db

    if we increse I by 50 % = (2.0 x 10^-7) x 1.5
    = 3.0 x 10^-7

    then
    10 log( 3.0 x 10^-7/1.00 x 10^-12) = 10 log (3.0 x 10^5) = 54.8 db

    so the change of decibel = 54.8db - 53db = 1.8db

    correct attemp this question this way??
     
  2. jcsd
  3. Sep 26, 2008 #2

    LowlyPion

    User Avatar
    Homework Helper

    Since the increase is by a factor of 50% you can also express the increase
    as simply 10log10(1.5) = 10*(0.176) = 1.76 db
     
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