No motor vehicles with an internal combustion engine shall be operated within the city unless the exhaust from such engine is muffled by a suitable and sufficient muffler.  No muffler cut-out or exhaust or vacuum whistle shall be used on any motor vehicle while operating within the city, except that exhaust whistles may be used on authorized emergency vehicles.
(`83 Code, § 15-304)  Penalty, see § 71.999