Kirkwood, MO Noise Ordinances: Vehicle Noise (2026)

Section 14-356, 'Vehicles producing noise,' opens with a flat ban on muffler cutouts, the aftermarket bypass valves that route exhaust around the muffler for a louder sound. It then sets a performance standard rather than a decibel number: no vehicle may 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. Every motor vehicle's engine must carry a properly attached muffler built with enough capacity to quiet the exhaust as completely as is done in a modern gas-engine passenger car, so a stock passenger vehicle is the benchmark an officer measures a loud exhaust against.

Any cutout or opening built into the exhaust pipe between the motor and the muffler must be completely closed and physically disconnected from whatever lever once operated it, and it has to be arranged so it cannot pop open automatically or be reopened while the vehicle is moving. 11 and was carried forward in substance when the Code was readopted in 2018. It sits in Chapter 14, Article VII, Division 1, alongside the City's headlamp and horn equipment requirements, and Kirkwood police enforce it as an equipment violation during traffic stops rather than through a separate noise-measurement program.