Going to sleep at 4:00 am is abnormal and you need to go to sleep much earlier. It's just unhealthy dude. I'd suggest hitting the sack around midnight the latest.
Start waking up really early by your standards for a few days. Put your alarm on at 6:00 or something and actually get your ass out of bed and go for a run or something. Do that for a few days straight and i bet your body will become naturally tired closer to a more sane hour. Then once you get used to going to sleep at 12:00 you can wake up at 8:00 and everythings fine.
Also if noise is an issue buy some of those orange/pinkish expandable ear plugs. They're comfortable enough for sleeping.