Answer
The intensity of an isotropic sound wave is
(d) inversely proportional to the square of the distance from the source
Work Step by Step
An isotropic sound wave propagates equally in all directions from the source. We can write an expression for the intensity:
$I = \frac{Power}{Area} = \frac{P}{\pi~r^2}$
The intensity of an isotropic sound wave is
(d) inversely proportional to the square of the distance from the source
