# B Sound Intensity Propagation and Sound Waves

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1. Dec 28, 2017

### Nunzio Luigi

Hello everyone, I'd ask you through an illustration which for me would be more clear to put questions I wrote in the image:

Thanks to all!
Cheers
Luigi

2. Dec 28, 2017

### BvU

Hello Luigi,

" Right ? " is not a good question to ask on PF. Just like "No" is not a good answer.

Sound waves do not 'respond to a law'. We describe what we observe from spherical sound waves by what we call an inverse square law. And the explanation is that the surface of a wave front increases with the square of the distance to the source (*). So whatever disturbance it is that propagates outwards: when it is twice as far away it has to disturb four times as much. Far enough from the source the disturbance can not be distinguished from random noise any more.

(*) the surface area of a sphere with radius $r$ is $4\pi r^2$​