It is not difficult to imagine why the intensity of a sound wave would follow inverse square law, as the spherical area increases as square of radius, all point sources of gravity, electrostatics and many more sources of energy follow the same law. When you think of newtonian gravitational force or electric force, all the formulae are classically parallel. What stands out, and therefore troubles me, is that the pressure of a wave, such as sound wave is said to follow a different proportionality, that of inverse distance law. That is the law followed by the energy terms because of integration, but they say that incase of sound, the intensity term follows inverse square while the pressure follows r^(-1) which is the whole thing in reverse connection. Being a man of science does come along with a man of doubt.