Sioux City, IA Noise Ordinances: Vehicle Noise (2026)

The Sioux City Municipal Code addresses vehicle noise through several intersecting provisions in Chapter 8.68. Section 8.68.030(12), 'Noisy Exhaust System,' makes the sound of any motor vehicle or recreational vehicle 'whose exhaust system has been modified by the installation of a muffler cut-out or bypass' a per se noise disturbance — enforceable at any hour with no decibel meter required. Section 8.68.030(4) targets engine repair, rebuilding, modification, or testing audible at the property line between 9:00 p.m. and 7:00 a.m. Section 8.68.030(11) prohibits the intentional screeching or squealing of tires in residential or commercial zones. Section 8.68.050(2) prohibits operating any motor vehicle stereo that is plainly audible at 50 feet or more from the vehicle without a sound equipment permit. Section 8.68.010(16)(e) carves out factory car radios used and intended for the occupants' enjoyment, provided the sound is not audible more than 50 feet from the vehicle. Iowa Code §321.436 (Mufflers, prevention of noise) backs all of this up at the state level: every motor vehicle on a highway must be equipped with a muffler in good working order, and no person may use a muffler cutout, bypass, or similar device. Sioux City Police enforce both the municipal and state provisions.