Damping of sound level vs. distance

Damping of sound level (decibel dB) vs. distance

Calculate 1/3-Octave-Band Filter

Calculate dBA from Octave Band Sound Levels

Adding decibels of one-third octave bands to level of one octave band and vice versa

Octave and one-third octave frequency bands

Butterworth Filters in C#

How to create 1/3-Octave-Band Filters in MatLAB/Octave