I have no clue about noise, but trains are close to 24/7. According to the Metro website, the first train leaves the nearby station at 3:59am during the week. The last train arrives at 1:51am. So, there's only a 2 hour windows without trains in the dead of night.

I still recommend calling the hotel and asking about whether trains are required to blow their horn and if the nearby crossing alarms can be heard into hotel guest rooms.