Sound is a wave. Waves can run into each other and cancel each other out (destructive interference) or they can essentially add onto each other and result in a larger wave (constructive interference). [Here’s](https://cdn.britannica.com/07/62907-004-A3A6351E.jpg) a graphic that shows both. Realistically, the waves won’t perfectly align to completely cancel each other out or double in size.
Your speakers emit sound waves throughout your room. These waves interfere with each other (as explained above) at different spots around the room.
So maybe the waves constructively interfere on the right side of the couch but destructively interfere on the left side. When you sit on the right side, the sound will be loud and clear, whereas the left side will sound quiet and muffled.
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