McHenry County, IL Noise Ordinances: Decibel Limits (2026)

16 (Noise Prohibited) was adopted by Ordinance O-201810-10-043 on October 16, 2018 and took effect December 15, 2018. 030 confines it to the unincorporated areas of McHenry County, so a home inside Crystal Lake, Woodstock or any other municipality is governed by that municipality's ordinance instead. 040 defines noise as sound, particularly amplified sound, whose volume, frequency, harshness, duration or timing causes unreasonable discomfort to inhabitants of ordinary sensitivities in the neighborhood or unreasonably interferes with the peace and comfort of neighbors, their guests or their customers.

050 then makes it an offense to knowingly make noise in such an unreasonable manner as to alarm or disturb another and provoke a breach of the peace. The section lists what an officer weighs: proximity to residential or commercial sleeping facilities, the land use and zoning of the source area, the nature of the receiving area, the time of day and duration, and whether the sound is recurrent, intermittent or constant. It closes with the sentence that matters for this page: in determining whether a sound is a prohibited nuisance noise, the use of a decibel meter or other measuring device is not required.

Two exclusions apply, for sound from authorized public programs or events and for sound from agricultural operations. 060 starts with a written warning; after that the State's Attorney may issue a notice of ordinance violation returnable in McHenry County Circuit Court, with a fine of $100 for a first offense and $100 to $1,000 for a second or later offense, each day counting as a separate offense, and injunctive relief available. Numeric limits exist only at the state level. Under 35 Ill. Adm. 102, amended effective November 1, 2018, a property-line noise source on residential, commercial or industrial land may not send sound onto receiving residential (Class A) land above the octave-band levels in the rule's tables, measured at least 25 feet from the source.

At 1000 Hz the nighttime ceiling is 35 dB from residential or commercial land and 41 dB from industrial land; the daytime ceiling at the same frequency is 45 dB and 52 dB. Those limits are enforced by the Illinois Pollution Control Board process, not by the county.