We only stayed for one night in Orio al Serio. The apartment is a 20mins walk from the airport. We could leave our luggage before the official check in time. That was really nice. It's obviously quite loud due to the closeness of the airport. But we had a good night sleep. Luckily we had to get up early because the church bells that started at 7am every 15 minutes wouldn't have let us sleep any longer.