This means that the daily early morning tooting across the street for the carpool is a violation. Dogs and motorcycles may also be singled out. The general rule is that it's unreasonable if it is, in the mind of an average person, too loud, prolonged or disturbing for the time of day. The child who practices the piano for an hour each day is certainly not a matter for the law. A roaring piano at 11 o'clock every night is.
Many towns also prohibit sustained noise that exceeds a certain decibel level.
The decibel limits are set according to the time of day and the neighborhood zoning. When a neighbor complains, police place decibel level monitoring equipment on an estimated property line and take a reading. If the noise level is too high, the person responsible will usually be warned. There are two common reactions to noise coming from a neighbor. The first is resignation.