The power plug timer can be really useful and moved around in different days. Blenders, TV, stereo that sort of stuff going off at particular times.
If you have a battery operated clock in the house get some flat batteries the same brand as the ones you use and occasionally put them in and set the clock to a particular time. Always the same time.
We got my friends roommates favourite Michael Jackson life size cut out and burnt it on the front lawn, poured olive oil down the hallway and surfed his surfboard down the hallway and into the kitchen.
I have a sneaky suspicion he knew it was us. Oh man that was one hell of a party…
I do like the child laughter idea. Don’t put it on repeat because that would allow the player to be found. Long delay, one of laughter, silence. That way you can do it again a few nights later and they won’t be able to narrow down where it’s from.