Answer:

Step-by-step explanation:
Assume a point sound source that emits a sound power P (in W) evenly in all directions of space. Let us also assume that the medium does not absorb this sound power when it passes through it. At a distance d from the source this power will have been evenly distributed over the surface of a sphere of radius d. Therefore, the acoustic intensity I at distance d will be worth:

This is the expression of the so-called law of the square of distance: "the intensity is inversely proportional to the square of the distance to the source (considered punctual)".
So





