Question

Most sound sources are considered point sources, and sound will spread spherically away from the source in the air. Consider the surface area of a sphere. What is the formula for the surface area of a sphere? If you don’t remember this, please look this up on the internet or in the reference section of your textbook. How does this explain the intensity of sound as you move away from a point source?  

Answer 1

The surface area of a sphere of radius ''R'' is given as : A= 4R²

let a sound source of power ''P'' emitting sound uniformly in the form of spheres surrounding to it.

At a distance ''R'' from the source, assuming a sphere of radius ''R''. Therefore the intensity of sound at the sphere is

I = P/ 4R²

Above formula explains that the intensity of sound varies inversely with the square of the distance from the source.