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Range of aduible sound
 10^14 : 1
 rocket going off : wind in trees

to test hearing we transfer the audlibe sound ratio into


100,000,000
x 1,000,000 =
 10^8 x 10^6 = 10^14
 8 + 6 = 14


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



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

decibel equation: dB spl
 dB SPL = 20 log (Pm / Pr)
 where:
 Pr = 20 uPa

Blaise Pascal
 French Scientist / Philoshopher
 1623  1662
 Physicist / Mathematician
 Measurement of atmoshperic pressure

dB SPL tells you...
how far away from the reference you are

0 dB SPL means
this is NOT 0, it means that you are at the reference

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

