The game engine is responsible for determining the obstruction and occlusion values, which it does using the position of the objects and listeners in relation to the game's geometry.
The obstruction and occlusion values for each game object affecting each listener must be passed down to the sound engine from the game programmatically.
In the Obstruction/Occlusion tab of the Project Settings dialog box, you can enable and define the default volume and Low Pass Filter (LPF) curves for obstruction and occlusion for each active platform in the project. Sound designers can also enable or disable the usage of any curve to best suit their performance and realism needs.
Using the curve of this snapshot, setting an obstruction value of 1.0f (100%) will produce a volume change of -50 dB on the source object.
It is a good practice to always define curves in a linear fashion to minimize CPU and memory usage in the project. Keep curves as simple as possible to begin with and customize only as needed.