Florissant, MO Noise Ordinances: Vehicle Noise (2026)

Section 380.140 sits in Chapter 380, Article II, Other Vehicle Equipment, and covers signaling devices and muffler noise together. Subsection A requires every motor vehicle to carry a working horn or whistle loud enough to warn other drivers and pedestrians, but limits it to warning use only; no other sound-producing signaling device is allowed at any time, so aftermarket horns, sirens or novelty noisemakers are off limits regardless of volume.

Subsection B is the muffler rule that actually drives most vehicle-noise complaints in Florissant. It bans muffler cutouts entirely and prohibits driving in such manner or condition that excessive and unnecessary noises are made by the machinery, motor, signaling device, or other parts, or by any improperly loaded cargo. Every motor must carry a properly attached muffler built to quiet exhaust noise as completely as is done in modern gas engine passenger motor vehicles, a standard the code ties to ordinary factory equipment rather than a decibel number. Where a car's exhaust pipe has a cutout or opening between the motor and the muffler, that opening has to be permanently closed and disconnected from any operating lever so it cannot pop open, whether automatically or by hand, while the vehicle is moving.

The Code sets no separate dollar penalty for Section 380.140, so a citation falls to the general penalty at Section 100.080: a fine of up to $1,000, up to three months in the city or county jail, or both. A Police Officer who stops a vehicle for a loud stereo, straight-pipe exhaust or disconnected muffler enforces this Section rather than a stand-alone noise ordinance, since Florissant folds vehicle noise into its vehicle-equipment chapter instead of the general nuisance provisions.