Sound attenuation can occur due to various phenomena. The most known are
- Distance: For a point source the sound pressure decreases by 6dB with each doubling of the distance to the sound source.
- Atmospheric absorption: Depending on the air pressure, humidity and tempreature sound attenutate increasingly faster if the frequency is higher.
However only accounting for those two attenuation types is probably not enough to simulate real world sound attenuation.
I suppose scattering with air molecules could also contribute to attenuation, but I did not find any clues or formula. Rayleigh or Mie Scattering is propably not applicable, since lightwaves have much shorter wavelengths than soundwaves.
Therefore my question is, what types of sound attenuation exist, if we suppose we are in open space and have direct line of sight between the audio source and listener, and what known mathematical models exist for them?