I experience the same on visionOS 27. I would expect a thin wall to lower the audio instead of completely blocking the sound. This is also what is described in the PHASE documentation: Set up occluder options for obstructed sound The framework lowers the volume of a sound source when an obstacle blocks its path to the listener. The result creates a realistic effect in cases where, for example, the player takes cover behind a gallery pillar, which reduces the volume of commotion from the other side of the room.