4am is unreasonable. On a Sunday-Thursday night, 10pm would be a reasonable cut-off for noise. On a Friday or Saturday night, 11pm would be OK. If they've given advance notice then I'd give them an extra hour, but anything beyond midnight is anti-social. Only had one that was really bad, a couple of years ago, when I called the council at 2am, and they eventually put a stop to the party at 4am. On that occasion, they really didn't care as it was a "going away" party for someone who was leaving the area.