331 4.1 Decibel

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Author:
shanamd2010
ID:
130645
Filename:
331 4.1 Decibel
Updated:
2012-01-30 12:41:14
Tags:
decibel
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Description:
CDO 331
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  1. Range of aduible sound
    • 10^14 : 1
    • rocket going off : wind in trees
  2. to test hearing we transfer the audlibe sound ratio into
    • a point system
    • 0 - 140
  3. 10^1
    10^2
    10^3
    • 10
    • 100
    • 1000
  4. 100,000,000
    x 1,000,000 =
    • 10^8 x 10^6 = 10^14
    • 8 + 6 = 14
  5. log2 =
    .30103
  6. 10^1.? = 80
    • 80 = 2x2x2x10
    • = log2 x log2 x log2 x log10
    • 10^.3 x 10^.3 x 10^.3 x 10^1
    • .3 + .3 + .3 + 1 = 1.9
    • 10^1.9 = 80
  7. Hertz
    Hz
  8. Decibell
    dB
  9. Alexander Graham Bell
    • teacher / scientist
    • 1847 - 1922
    • works with deaf
    • work lead to telephone / aviation
    • Scottich immigrant to Canada
    • married a deaf women
    • bffs with Helen Keller
    • wanted to switch to the phonetic alphabet
    • forbid signing
    • thought the deaf and blind should not reproduce
  10. decibel equation: dB spl
    • dB SPL = 20 log (Pm / Pr)
    • where:
    • Pr = 20 uPa
  11. Blaise Pascal
    • French Scientist / Philoshopher
    • 1623 - 1662
    • Physicist / Mathematician
    • Measurement of atmoshperic pressure
  12. dB SPL tells you...
    how far away from the reference you are
  13. 0 dB SPL means
    this is NOT 0, it means that you are at the reference
  14. Pm = 8,000 uPa
    dBspl = ?
    • dBspl = 20 log(Pm/Pr) Pr = 20uPa
    • = 20 log (8000/20)
    • = 20 log (400) 400=2x2x100
    • = 20 (2.6) 400=10^.3 x 10^.3 x 10^2
    • dBspl = 52 400=10^2.6

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