Hi,
Unfortunately, we do not currently have a simple occlusion system for Unity. I will pass this suggestion on to our developers to look into it further.
However, we do have a Geometry System (FMOD API | Core API Guide - 3D polygon based
occlusion) which can be accessed through the Core API. An alternative is using a line cast from the emitter to the listener done so here: Audio Occlusion FMOD w/ Unity not working - #2 by Connor_FMOD which checks for line of sight and manipulates the attenuation values accordingly.
Hope this helps!