A year ago, it came out that even though his house is right there, there is a noisy water fountain or such in between, and he heard nothing that night.
Does anyone know whereabouts this Frank the caretaker's house is in OP's grounds? The grounds of OP's house isn't particularly big and I can't see any outbuildings in the overhead shots, unless I've missed something somewhere .. I also can't see any kind of fountain in the grounds, either ..