A. Noise Measurement. Regulations .04 through .12 apply to the measurement of noise of any:
(1) Motor vehicle while in motion;
(2) Stationary motor vehicle equipped with an engine governor; and
(3) Stationary motor vehicle without an engine governor.
B. Noise Exemptions. These regulations do not apply to:
(1) The sound generated by a horn or other warning device when operated under the provisions of the Transportation Article, §22-401, Annotated Code of Maryland;
(2) The sound generated by an emergency motor vehicle when operating under the provisions of the Transportation Article, §22-106, Annotated Code of Maryland;
(3) The sound generated by transit and school buses.