Check with  the Police Department ask for a Captain or a Lieutenant and ask if there is a city ORDINANCE regarding Loud Noise, if there is call the cops and make sure they know there is a city ordinance, make them to write a complaint record, every person has the right to live peacefully. According to what I understand every City has an ordinance regarding Loud noise, like music, dog barking, car horns..Keep pounding the Cops to do something about it don't give up...forget about the decibels..go for the police report and make sure they know you will take them to court, loud noise can bring a lot of stress, and emotional problems and behavior... good luck