Not sure how much this will help, but, last night, I woke up ~1-2h after I feel asleep and could feel the bed kinda moving under me in the area where my back was. It was an interesting feeling though Anyways, I would say that fear plays a big part in SP experiences. If you go into SP and KNOW that there is nothing to fear, then you will not see anything and possibly not hear anything either, just some food for though