How to derive the Sperically symmetric Wave Equation (in spherical coordinates) using first principles?

Question

I want to use first principles (of mass and momentum conservation) on a spherical shell and derive the wave equation given below, where $p'$ is the pressure perturbation :

$\frac{\partial^2 p'}{\partial t^2} = \frac{c^2}{r^2}\frac{\partial}{\partial r}\left(r^2\frac{\partial p'}{\partial r} \right) $