conversion from dB

Discussion in 'Homework Help' started by u-will-neva-no, Jan 11, 2012.

  1. u-will-neva-no

    Thread Starter Member

    Mar 22, 2011
    230
    2
    Hello everyone,

    there should be a relatively easy solution to this but I can't get the correct answer.

     20\log_1_0(x) = 20dB

    How do I find x?

    I try to rearrange (taking the exponential of both sides but that does not work). Am I suppost to change the RHS (20dB)?
     
  2. joeyd999

    AAC Fanatic!

    Jun 6, 2011
    2,686
    2,749
    how about divide by 20 first?
     
  3. Jony130

    AAC Fanatic!

    Feb 17, 2009
    3,957
    1,097
    First step

     \frac{20dB}{20} = 1

    Second step

    10^1 = 10

    So the x = 10

    for 25dB

     \frac{25dB}{20} = 1.25

    10^{1.25} = 17.7827941
     
    u-will-neva-no likes this.
  4. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
    6,357
    718
    Wiki covers it well

    The part where people get caught up is when to use 10 log or 20 log for dB. When measuring voltage or current gain, use 20 log, when measuring power gain, use 10 log.

    It is also good to remember the conversion for dB/Octave <-> dB/Decade (left as an exercise for student)
     
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  5. u-will-neva-no

    Thread Starter Member

    Mar 22, 2011
    230
    2
    Brilliant, thank you Jony130 and thatoneguy !! :)
     
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