Lost a tenant due to horrible neighbor

[Hkd Lawrence]

We own a nice semi-detached home in a good neighborhood on the outskirts of Baltimore City.  Our tenant just informed us that she is terminating her lease due to a contentious relationship with the neighbor she shares a wall with.  The neighbor has 3 large dogs and plays music at loud levels all day and night.  I personally witnessed some of the neighbor's bad behavior prior to leasing the property but I attributed the behavior to the idea that the house was empty before I bought it and that he would respect the fact that someone was now living next door.  Now I'm losing a GREAT tenant because she refuses (rightfully so) to put up with the guy.  

Any suggestions on how to deal with the neighbor in the future would be greatly appreciated.