A data center in unincorporated Los Angeles County must not push exterior noise above 50 dBA daytime or 45 dBA at night at a neighboring residential property line under County Code Section 12.08.390. Industrial-zoned receptors allow up to 70 dBA.
The Los Angeles County Noise Ordinance (County Code Section 12.08.390, Ordinance No. 11743) sets exterior noise limits at the receiving property, not the source. Cooling systems, chillers, and backup generators at a data center are measured where the noise lands: 45 dBA in noise-sensitive areas, 50 dBA daytime and 45 dBA nighttime at residential property, 60 daytime and 55 nighttime at commercial property, and 70 dBA anytime at industrial property. Limits tighten with duration — the base level may not be exceeded more than 30 minutes per hour, with higher short-burst ceilings — and pure-tone or impulsive noise is penalized 5 dBA.
Noise exceeding the Section 12.08.390 limits at a neighboring property line is a violation subject to County citation and abatement; the County can require mitigation and withhold approvals until measured sound conforms.
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