Is there anything I can do to protect my tenants' rights when a neighbor is threatening them for a perceived noise violation?

Current tenants in my rental house have band practice in the bsmt 2 evenings a wk & are ALWAYS done well before 10:00pm. I put a notice on doors of neighbors informing that we're doing some sound proofing to min. any impact & requesting they call w/ feedback (#'s provided). The one neighbor called, yelling there is no compromise/solution other than NO practicing at all - EVER. He has since screamed at the tenants who are trying to be respectful & called the police. I drove over to be there when police arrived & was told they would "keep this infomal": there had been a complaint & there was nothing they could do until 10:00pm. They didn't even go to the neighbors' house but I did to try to resolve w/out success. Tenants are now feeling they should move which creates hardship for all of us.