At a distance r0 = 20.0 m from a point isotropic source of sound the loudness level Lo = 30.0 dB.

Question

At a distance r₀ = 20.0 m from a point isotropic source of sound the loudness level L₀  = 30.0 dB. Neglecting the damping of the sound wave, find: 

(a) the loudness level at a distance r = 10.0 m from the source; 

(b) the distance from the source at which the sound is not heard.

Answer 1

(a) As there is no damping, so

(b) Let r be the sought distance at which the sound is not heard.

Thus for r > 0. 63 km no sound will be heard.