S.C. Code Ann. § 56-5-4950: Horns and warning devices.

Every motor 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 two hundred feet, but no horn or other warning device shall emit an unreasonably loud or harsh sound or whistle. No vehicle other than an authorized emergency vehicle shall be equipped with nor shall any person use upon any such vehicle any siren, whistle or bell.