N.J. Stat. § 39:3-69
Every motor vehicle except a motor-drawn vehicle when operated upon a highway shall be equipped with a horn in good working order and capable of emitting sound audible under normal conditions from a distance of not less than 200 feet, but no horn or other warning device shall emit an unreasonably loud or harsh sound or a whistle. The driver of a motor vehicle shall, when reasonably necessary to insure safe operation, give audible warning with his horn but shall not otherwise use such horn when upon a highway.
No vehicle shall be equipped with nor shall any person use upon a vehicle any siren, whistle or bell except as otherwise permitted in this section. It is permissible but not required that any vehicle be equipped with a theft alarm signal device which is so arranged that it cannot be used by the driver as an ordinary warning signal. Any emergency vehicle authorized by the commission may be equipped with a siren, whistle, or bell capable of emitting sound audible under normal conditions from a distance of not less than 500 feet and of a type approved by the commission, but such siren, whistle or bell shall not be used except when such vehicle is operated in response to an emergency call or in the immediate pursuit of an actual or suspected violator of the law, in which said latter events the driver of such vehicle shall sound said siren, whistle or bell when necessary to warn pedestrians and other drivers of the approach thereof.
No person shall install or use on the exhaust system of any motor vehicle any device which emits an audible sound unless authorized to do so by the commission.
No bicycle shall be equipped with nor shall any person use upon a bicycle any siren or whistle.
The commission is hereby authorized in its discretion to promulgate standards concerning the audibility of audible warning devices.
N.J.S. § 39:3-69