Cook County, IL Noise Ordinances: Decibel Limits (2026)
Key Facts
- Governing section
- Zoning Ordinance § 6.1.9(E)(4)(a)
- Applies to
- I-1 through I-4 industrial districts
- Scope
- Unincorporated Cook County only
- Enforced by
- Dept. of Building and Zoning
- Peak impact noise limit
- 86 dB at adjacent lot line
Summary
In unincorporated Cook County's I-1 through I-4 industrial zoning districts, plants can't exceed set octave-band decibel limits at residential district boundaries or adjacent lot lines, with stricter nighttime caps enforced through the zoning performance-standards process.
4.Industrial performance standards. Uses shall comply with the following standards:a.Noise. ... shall be used with the following tables: At no point along the boundary of a residential district or along an adjacent lot shall the sound pressure level of any operation or plant exceed the decibel limits in the octave bands designated below.
Full Breakdown
Cook County's zoning ordinance caps industrial-source noise using nine octave bands, from 31.5 Hz to 8,000 Hz. Daytime (7 a.m.-10 p.m.) limits run as high as 79 dB at an adjacent lot line and drop to 40 dB at 8,000 Hz; nighttime (10 p.m.-7 a.m.) limits are lower across the board. Impact noise can't exceed 86 dB peak at a lot line. The rule applies in the I-1, I-2, I-3 and I-4 industrial districts of unincorporated Cook County and is enforced through the County's performance-standards complaint and investigation process, not a fixed inspection schedule. Construction noise, moving-vehicle noise and emergency signals are exempt.
Violations & Fines
A substantiated complaint can force the operator to alter equipment or operations, and the County can void industrial building permits and charge the violator for any outside acoustic consultant it hires to investigate.
Frequently Asked Questions
Does this noise standard apply inside Chicago or suburban cities?
What happens if an industrial noise complaint is substantiated?
Sources & Official References
Other rules in Cook County
Compare Cook County to another location·View the Illinois noise ordinances overview
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