Obstacles in the environment, such as large objects, or walls, also alter the way we perceive sound. We can often hear a person speaking in an adjacent room, but the sound is not as clear as if they were standing next to us. The reason for this is that although sound can pass through several types of materials, it loses energy and several of its higher frequencies during the process. This results in a quieter, muffled sound. There are two techniques used to simulate obstacles in 3D audio: obstruction and occlusion.
Obstruction occurs when the source and the listener are in the same environment, and there is an obstacle in the way, but there is still enough space around the obstacle for the sound waves to flow. In this situation, sound waves passing directly through the obstacle are attenuated and filtered, but reflected sound waves are not affected.
Occlusion occurs when the source and listener are in different environments, and all the sound needs to go through...