Someone from this number used to always call me and play a very loud 3500 Hz tone into the phone. We had to stop screening our calls because at very early hours of the morning they would play that awful sound and it would fill the house.
The police can't do anything about calls like this. The best they can do is tell you to call the phone company and the best the phone company can do is tell you to *57 the call. If the same number calls you more than 3 times per day or 5 times per week then you can press "phone harassment" charges. Pranksters usually know this and don't call from the same number twice. How recently did you get these calls? This number shows up on phonebook.com, so you could always call the number back and either confront the prankster or ask someone else at that number to try and put a stop to the calls.