Can you make your own probes or nodes? (Pathfinding and Audio)

Hi,

I've been interested in making more realistic audio and I've come to a brick wall on this specific issue: diffraction/obstruction. It's when the audio source will appear to come from a doorway, for instance, rather than a straight line from the source to the player.

Someone has made this in Unity and made an asset (https://www.assetstore.unity3d.com/en/#!/content/40200). He uses 'Nodes' or 'Probes' (he names them differently in certain videos) to define where the audio can play from. All of these objects are 'connected' and seem to help with some kind of pathfinding. But he never explains how he does it (understandably), but I'd like to have a go myself and I have no clue what these probes or nodes are, or how he made them. Also, of course, the audio source is then being moved and still having the normal volume drop off.

Also, Rainbow Six Seige uses a similar system and called their objects 'Propagation Nodes'.

Would anyone be able to help with explaining this? Or at least pointing me in the right direction so I can teach myself.

Thanks in advance, James