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Sound pressure level magnitude question.

  1. Feb 1, 2006 #1
    Hey all,

    I've got an audio related question for you guys/gals:

    I understand the logarithmic relationship to SPL, but would someone help me out with a simple question and post a formula as to how you arrive at an answer? Assuming a start value of 150 decibels, what pressure level would represent a magnitude of 1000 times increase over 150dB?

    -As a side note, cool forum! Everything from mathematics to religion and alien abduction; you don't find that often! I'm sure I'll be spending too much free time reading threads in the future. :biggrin:

    Thanks!
     
  2. jcsd
  3. Feb 1, 2006 #2

    rbj

    User Avatar

    do you mean, what dB level for 1000 times more sound pressure? or what is the pressure level for 150,000 dB :eek: (i think 150,000 dB SPL will liquify everything.)

    i don't deal with the alien abduction and haven't seen any religion here.

    but i don't do all of the forums.
     
  4. Feb 1, 2006 #3
    Right on the first part.......what sound pressure level would be 1000 times more spl than 150db.

    It's down in the Lounge and Philosophy sections.
     
  5. Feb 1, 2006 #4
    No one? :confused:
     
  6. Feb 1, 2006 #5

    rbj

    User Avatar

    well, think of pressure like voltage and particle velocity like current. for example, a spherically expanding sound wave will obey the inverse-square law as far as power (more specifically, intensity, which is power per unit area) so the power or intensity is reduced by a factor of 4 (or and additive gain of -6.02 dB) every time the distance from the point source is double. also, for a sound wave front, the r.m.s. pressure times the r.m.s. particle velocity (the component of the particle velocity that is in-phase with the pressure wave) multiply to be intensity, and it also turns out that both are 1/r. so to reduce the magnitude of the pressure wave by a factor of 1000, i would have to increase my distance by a factor of 1000, which means i double it about 10 times (210 = 1024) so that would be about 60 dB. (in fact it would be exactly 60 dB if you look at the exact definition of dB.) so i guess your answer is 210 dB which is so friggin' loud, only a martyr or a masochist would be willing to be subjected to it. 0 dB is roughly the threshold of hearing and 130 is roughly the threshold of pain and 150 dB is louder than anything i would ever want to hear.
     
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