Delaware Code
Subchapter I. Equipment Requirements
§ 4306. Horns and other sound devices; unlawful use.

(a) Every motor vehicle when operated upon a highway shall be equipped with a horn in good working order capable of emitting sound audible under normal conditions from a distance of not less than 200 feet.
(b) Except as otherwise provided, no vehicle shall be equipped with and no person shall use upon a vehicle any siren, exhaust, compression or spark plug whistle. The driver of a vehicle shall, when reasonably necessary to insure safe operation, give audible warning with the horn but shall not otherwise use the horn for any other purpose. No driver of any vehicle shall use a horn:

(1) To make unreasonably loud or harsh sound;
(2) When stationary; or
(3) When passing an animal-drawn vehicle or bicycle under normal conditions where no imminent danger of a collision exists.
(c) No person operating or occupying a motor vehicle on any street, highway, alley, or parking lot shall operate or permit the operation of any music amplification system, including, but not limited to, any radio, tape player, compact disc player, or any other electrical device used for the amplification of music in or on the motor vehicle so that the sound is plainly audible at a distance of 50 or more feet from the vehicle. For the purpose of this subsection, “plainly audible” means any sound which clearly can be heard by unaided hearing faculties, however, words or phrases need not be discernible and bass reverberation alone shall be sufficient to so constitute.
(d) Subsection (c) of this section shall not apply to those in a parade which has been issued a permit nor to commercially licensed vendors in the legitimate operation of their businesses.
(e) Subsection (c) of this section shall not apply to any municipality of this State with a population in excess of 50,000 which has an ordinance addressing noise violations of that type. In the event that any such municipality repeals its ordinance without substituting requirements at least as restrictive as those found in subsection (c) of this section, then the provisions of subsection (c) of this section shall take effect within that municipality.

Structure Delaware Code