Every morning my storage / airing cupboard makes this noise:
It's been doing it about two months now, almost at 7am every day! Today's the first day I managed to capture it!
It's a communal heating system, there's a cylinder and a few pipes in the cupboard, and the noise seems to coming from an old capped off iron pipe, but because it's a vibration it could be coming from anywhere.
I'm currently waiting for the council to call me back!