# Formula for sound dissipation in air?

1. Feb 28, 2012

### Ralphonsicus

Is there an equation that deals with the dissipation of sound waves in air? As in, how much they die out with distance, because we know they must, otherwise you could hear me talking now!

2. Feb 28, 2012

### Hobold

The intensity is inversely proportional to the radius squared.

That is, if a certain source has a power P and it emits pressure waves spherically, the intensity I you'll hear is

$$I = \frac{P}{4\pi r^2}$$

3. Feb 29, 2012

### sophiecentaur

There is also some absorption, which depends on frequency (proportional to frequency squared) and humidity. This produces an attenuation which is proportional to distance (as opposed to inverse square law). Both effects occur at the same time.