At a busy street corner, the sound level is 75dB.

Question

What is the intensity of sound there? (Take threshold of hearing Io=1.0×10^-12W/m²?

Answer 1

10*Log(I/Io) = 75 db.
10*Log(I/1*10^-12) = 75,
Log(I*10^12) = 7.5,
I*10^12 = 10^7.5,
I = 10^7.5/10^12 = 1*10^-4.5 = 3.16*10^-5 W/m^2.