Md. Code, Transportation § 21–1122

(a) In this section, “sound amplification system” means a compact disc player, a radio, a tape player, or a similar device.

(b) This section does not apply to:

(1) Authorized emergency vehicles;

(2) Vehicles operated by communications, electric, gas, or water utilities;

(3) A sound amplification system operated to request assistance or to warn of a hazardous situation; or

(4) Unless otherwise prohibited by local law, a sound amplification system used for advertising, parades, or for political or other special events.

(c) When a motor vehicle is being operated on a highway, the driver of the vehicle may not operate or permit the operation of a sound amplification system from the vehicle that can be heard outside the vehicle from 50 or more feet.

(d) A violation of this section is not considered a moving violation for purposes of § 16–402 of this article.