My husband was sleeping on the couch last night and facing the back of the couch curled up. He woke up to hearing this really loud knocking but coming from behind him. It got louder and lounder and closer to him but he couldn't move, the knocking was so intense that he could feel it almost like vibrating. He found himself locked in the position he was lying in and couln't speak or move to see what it was behind him. The knocking stopped but then came this flapping noise almost like someone had taken a blanket or something and started shaking it up and down real fast to make this flapping noise. He said it started slow then got real fast and real close to him, however he still coundn't move. He was struggling to move and once the noise stopped he was able to turn. There was nothing there. He is very upset and freaked out by this, can anyone tell me what they think this might have been or why this happened?