As used in this chapter:
(a) "Aircraft" means any contrivance now known or hereafter invented, used or designated for flight in the air, including airplanes, helicopters, lighter-than-air dirigibles and balloons.
(b) "Sound-amplifying equipment" means any machine or device used for the amplification of the human voice, music or any other sound, but not including standard radios when used and heard only by occupants of the vehicle in which they are installed, warning devices on authorized emergency vehicles and horns or other warning devices used only for traffic safety.
(c) "Sound truck" means any motor or horse-drawn vehicle having mounted thereon, or attached thereto, any sound-amplifying equipment.
(1977 Code § 9-1701)