St. Louis, MO Noise Ordinances: Vehicle Noise (2026)

307.170. Other equipment of motor vehicles — violations, penalty. — 1. Signaling devices: Every motor vehicle shall be equipped with a horn, directed forward, or whistle in good working order, capable of emitting a sound adequate in quantity and volume to give warning of the approach of such vehicle to other users of the highway and to pedestrians. Such signaling device shall be used for warning purposes only and shall not be used for making any unnecessary noise, and no other sound-producing signaling device shall be used at any time. 2. Muffler cutouts: Muffler cutouts shall not be used and no vehicle shall be driven in such manner or condition that excessive and unnecessary noises shall be made by its machinery, motor, signaling device, or other parts, or by any improperly loaded cargo. The motors of all motor vehicles shall be fitted with properly attached mufflers of such capacity or construction as to quiet the maximum possible exhaust noise as completely as is done in modern gas engine passenger motor vehicles. Any cutout or opening in the exhaust pipe between the motor and the muffler on any motor vehicle shall be completely closed and disconnected from its operating lever, and shall be so arranged that it cannot automatically open, or be opened or operated while such vehicle is in motion. [...] 10. Violation of this section shall be deemed an infraction.