When I'm awake at late-night, I sometimes hear children laughing in the corridors of my apartment.
It sounds similar to how it does in the day, which means that it's neither quiet enough for me to not hear, nor loud enough to disturb me.
Usually, it's only for a minute or two, and I can ignore it if I want to, since it doesn't scare me that much.
I've heard it enough to know that it's harmless, paranormal or not.