I've been in my apartment for over 3 years and I've never had any problems, until about 2 weeks ago. I woke up at 6am on a Sunday morning to music playing from an adjacent unit. The insulation between units is pretty good so they must have had the radio turned up. Last week, a non-resident was parking in resident's assigned spots, including mine. About an hour ago (it's 1:53am), someone started watching TV and I could hear it while in bed.
No new tenants moved in, but my neighbor had a "friend" show up two weeks ago. I suspect I know the cause of the problems.