Problem 4.183

At a distance $r_{0}=20.0 \mathrm{~m}$ from a point isotropic source of sound the loudness level $L_{0}=30.0 \mathrm{~dB}$. Neglecting the damping of the sound wave, find: (a) the loudness level at a distance $r=10.0 \mathrm{~m}$ from the source; (b) the distance from the source at which the sound is not heard.