Occlusion
Also said as Muffling through walls, Obstruction, Sound propagation
Muffling a sound because something solid stands between it and the listener, usually with a low-pass filter and a drop in volume. Games test this with lines or room graphs.
In any game with hearing, it tells players where something is relative to the walls. Without it, enemies in the next room sound as if they are beside you.
Say it
“If there is no clear line from the sound to the listener, close a low-pass to 500 Hz over 100 ms and drop it 9 dB. Check each door when it opens.”
Where you’ve seen it
Rainbow Six Siege passes sound through propagation nodes and destructible connection points, so breaking a wall changes what you hear. Its audio director Louis Philippe Dion separated occlusion from obstruction, because occlusion alone would have let players hear through walls too well.
Not to be confused with obstruction
Trade usage varies, but occlusion usually means the sound and the listener are in separate spaces, with the sound passing through the wall. Obstruction means something blocks the direct path while the sound still reaches you around it.