Maryland Code, Transportation § 22-401.1

(1) Operated by mechanical or electrical means or by any means other than manually;

(2) Amplified by any electrical or electronic means;

(3) Capable of emitting sound audible under normal conditions from a distance of more than 400 feet;

(4) Used for any purpose between the hours of 10 o'clock p.m. and 8 o'clock a.m.; or

(5) Used as an ordinary warning signal at any time.