For a simple noise complaint, no. Only time I would drop the door w/o a warrant would be if there was a substantial chance of death or serious injury. Opening the door and walking into someone else's house on a simple noise complaint is a good way to get your a$$ shot
How did they get in? If the door was unlocked or open, they can go in to see what is wrong, or if someone is injured, or to check if someone was hiding. But they can't go in and start going through your belongings with out a warrant. The complaint was about your place so of course they can go in-how else can they snag you?
RetiredKop is correct, the police have no right to enter your property without either (1) permission or (2) a warrant issued by a judge. As he noted, if they see someone in imminent peril they have the right to rescue them, but a noise complaint (unless it was explosions) absolutely not.