What to do about rowdy neighbors

[Matt Slease]

I have a rental in a decent neighborhood, but the house next door has now scared away 2 of my tenants.

People coming and going all hours of the night, screaming fights during all hours of the day and night, inside and outside the house, to the point where it would wake up every neighbor on the block.  Other neighbors have called the police many times but this has been going on for at least as long as I've owned the house (8 months).

Thinking of finding out who owns the house and trying to buy it, but what else can be done about neighbors like this?  Just had a great tenant move out because she feels unsafe.