75 Pa.C.S. § 4535: Audible warning devices.

(a) General rule.--Every motor vehicle operated on a highway shall be equipped with a horn or other audible warning device of a type approved in regulations of the department.

(b) Certain sound devices prohibited.--Except as specifically provided in this part or by regulations of the department, no vehicle operated on a highway shall be equipped with a siren, bell, whistle or any device emitting a similar sound or any unreasonably loud or harsh sound.

(c) Exceptions.--This section shall not apply to any special mobile equipment, commercial implement of husbandry or implement of husbandry that is not so equipped by the original manufacturer.