Noise Measurement. Regulations .04 through .12 apply to the measurement of noise of any: Motor vehicle while in motion; Stationary motor vehicle equipped with an engine governor; and Stationary motor vehicle without an engine governor. Noise Exemptions. These regulations do not apply to: 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; The sound generated by an emergency motor vehicle when operating under the provisions of the Transportation Article, §22-106, Annotated Code of Maryland; The sound generated by transit and school buses.