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

McLean County Code § 350-43XX(2) sets the county's one numeric decibel standard in its zoning use regulations: a small wind energy system, permitted by right under § 350-43XX, cannot exceed a noise level of 60 decibels as measured at the closest property line. The ordinance carves out a narrow exception, allowing the noise level to be exceeded during short-term events such as utility outages or severe wind storms, when the turbine's operating characteristics change outside the owner's control. This decibel cap sits inside a fuller set of small wind system standards: a setback equal to 110% of system height from all adjacent property lines and road, railroad and utility rights-of-way; a construction permit application with engineer-certified structural drawings; FAA notification for towers near airports; and a maximum blade-to-ground clearance requirement of 15 feet.

Height itself is separately capped by acreage and district, from 50 feet on parcels under one acre to 150 feet on five-acre-plus parcels in agricultural, commercial or manufacturing districts (80 feet in R-1 and R-2 districts regardless of acreage). Other uses in the county code reference noise only by cross-reference to the Illinois Pollution Control Board's standards rather than a county-set decibel figure, making § 350-43XX(2) the code's specific numeric limit. The rule applies to unincorporated McLean County; Bloomington and Normal set their own noise standards inside city limits.