Answer:
The intensity increases by a factor 9
Explanation:
The intensity of a sound wave follows an inverse square law, that means that it is inversely proportional to the square of the distance:
[tex]I\propto \frac{1}{r^2}[/tex]
where r is the distance from the source.
In this problem, the distance from the source is reduced by a factor 3, so the new distance is
[tex]r'=\frac{1}{3}r[/tex]
this means that the new intensity will be
[tex]I' \propto \frac{1}{r'^2}=\frac{1}{(\frac{1}{3}r)^2}=9\frac{1}{r^2}=9I[/tex]
So, the intensity will increase by a factor 9.
