# LogAnswers - Examples of working with logarithmic functions...

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Examples of working with logarithmic functions All work with the definition of dB: dB = 20log 10 (P/P ref ). SPL = 20log 10 (P/P ref ), where P ref = 20 micropascals (20 μ Pa) And the basic knowledge that if 10 x = y, then log 10 (y) = x . Telephone problem (absolute SPL calculations) 1) The amplitude of the sound pressure wave generated by a particular telephone ringing is 0.2 Pa. What is the sound pressure level? Given an sound intensity, P, calculate the SPL (relative to the standard reference, 20 uPa). SPL (dB) = 20log 10 (P/P ref ) = 20log 10 (0.2/0.00002) = 20log 10 (10,000) = 20*4 = 80 dB 2) The sound pressure level of a telephone ringing is 80 dB. What is the physical amplitude of the sound wave? Given a SPL, calculate the amplitude of the sound pressure wave. . SPL (dB) = 20log 10 (P/P ref ) => 80 = 20log 10 (P/0.00002) => 4 = log 10 (P/0.00002) => 4 = log 10 (P/0.00002) => 10 4 = P/0.00002 => P = 0.00002 x 10 4 = 0.2 Pa Earplug problem (relative SPL) . Using these two facts, answer the following questions:

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LogAnswers - Examples of working with logarithmic functions...

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