Cook County Chapter 38 environmental control rules and Illinois Pollution Control Board Part 901 set octave-band sound limits that capture low-frequency bass through 31 Hz and 63 Hz bands. dB(C) measurements supplement dB(A) when complaints describe rumble or thumping bass.
Cook County Chapter 38 incorporates Illinois Pollution Control Board Part 901 numeric noise standards, which prescribe octave-band sound pressure level limits at the receiving land's property line, including bands centered at 31.5 Hz, 63 Hz, and 125 Hz that capture low-frequency bass. Inspectors typically supplement A-weighted measurements with C-weighted (dB(C)) readings when complaints describe bass thumping from nightclubs, residential subwoofers, or commercial sound systems. The dB(C) – dB(A) differential above approximately 10 dB indicates dominant low-frequency content. Cook County Department of Environmental Control and Illinois EPA share enforcement; municipalities may add subjective plainly-audible bass standards but state numeric octave-band limits remain the floor.
Exceeding IPCB Part 901 octave-band limits in low-frequency bands (31.5 Hz, 63 Hz) at a residential property line is a Cook County Chapter 38 violation. Daily fines apply; repeat commercial offenders face permit suspension and municipal citations.
See how Cook County's low-frequency bass limits rules stack up against other locations.
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