Mount Prospect, IL Noise Ordinances: Decibel Limits (2026)

Mount Prospect prints numeric sound limits in its zoning code for industry, and they attach to the I-1 limited industrial district. Section 14.2104 G.1 says no industrial activity shall generate noise across any residential or business zoning district boundary line in excess of the levels shown in Table I, nor shall the noise exceed seventy one (71) dBA when measured on the A-weighted scale.

Table I sets a level in decibels for each octave band center frequency, with one column for daytime, 8:00 A.M. to 10:00 P.M., and one for nighttime, 10:00 P.M. to 8:00 A.M. At 31.5 hertz the limits are 72 by day and 67 at night. At 63 hertz they are 67 and 66, at 125 hertz 66 and 65, at 250 hertz 59 and 52, at 500 hertz 52 and 46, and at 1000 hertz 46 and 40. At 2000 hertz they drop to 40 and 35, at 4000 hertz to 38 and 35, and at 8000 hertz and over to 38 by day and 32 at night.

The code specifies how the noise is measured. Sound levels are taken with a sound level meter and octave band analyzer to meet the criteria for the noise measurement provisions of OSHA, and they must conform to ANSI S2-4 of the American National Standards Institute.

The noise limit is one of the performance standards in Section 14.2104 G, alongside vibration limits, smoke and particulate matter limits, and fire and explosion hazard limits. No use established in an I-1 limited industrial district shall be operated so as to exceed the standards, and a use already established can be altered, enlarged, expanded or modified provided that all performance standards of the district are met. Table I is an industrial performance standard for the I-1 district. It is not a household noise limit.