the most sensitive human hearing occurs at about 1000 Hz and corresponds to sound pressure of 0.0002 microbar.

Question

(0.0002 microbar = 0.0002 millionths of an atmosphere.)

The sound of a nearby jet engine is typically 130 decibels referred to that sound pressure.What is the engine's sound pressure in bars(atmospheres)??

Answer 1

a db is defined as:

dB = 10*log(Q/Qref) where Q is some qunatity and Qref is the reference value. In the above problem Qref = 0.0002 microbars and

130dB = 10*log(Q/Qref)

13 =log(Q/Qref) . Now treat each side as the argument of 10^p -

10^13 = 10^log(Q/Qref) = Q/Qref

Q= 10^13*Qref = 10^13 * 10^-10 bars = 10^3 Bars