Answer to Question #2278 in Acoustics for shallen

Question

The sound of heavy automobile traffic, heard at a certain distance, has a sound level of about 75 dB. What is the intensity of the noise there? answer in W/m^2.

Answer 1

The measure of a ratio of two sound intensities is
L₁=10 log₁₀(I₁/I₀)
where I₁ and I₀ are the intensities.
So, we have
75=10 log₁₀(I₁/I₀ ) → log₁₀(I₁/I₀ ) = 75/10 → I₁/I₀ = 10^7.5 = √(10¹⁵ ) W/m²
The sound intensity level is given the letter "L₁" and is measured in "dB". The decibel is a dimensionless quantity.