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Franklin County work group proposes frequency‑band sound rules and monitoring for data centers, flags pressure‑wave concerns
Summary
The work group recommended replacing single averaged dB metrics with octave‑band measurements, a 125‑foot measurement point, tonal penalties and 3D pre‑development modeling; members urged language to capture inaudible pressure waves and annual audits with penalties for noncompliance.
Franklin County staff on Feb. 2 proposed a detailed sound‑standards approach for data centers that would require frequency‑band measurements, pre‑development 3‑D modeling and ongoing monitoring — and the group debated how to address inaudible low‑frequency pressure waves that communities elsewhere have reported.
Presenter (staff member) said the draft adds octave‑band measurements rather than relying on single averaged decibel figures, because ‘‘if you take an average… some of these outliers that are really annoying can be missed.’’ The draft also specifies measurement at a point 125 feet beyond the facility’s property line, daytime and nighttime thresholds, and a tonal penalty that reduces allowable limits for distinct tones.
On sub‑threshold phenomena: several members and public commenters raised concerns about inaudible pressure waves and vibration that can cause sleep disruption and other effects. Brian and Tracy pushed to include wording for ‘‘pressure waves’’ and vibration in the performance and remediation sections; staff said the draft already requests an environmental and nuisance mitigation study that includes vibration and EMI and that remediation would be required where studies show problems.
Enforcement and modeling: the work group discussed requiring certified acoustic analyses prepared by licensed engineers using industry‑standard software with a 3‑D component to model elevated sources (rooftop chillers/exhausts). Presenter said remediation options could include acoustical blankets, bafflers or soundwalls and cited a corrective action provision with example penalties — including a daily fine after a notice period and possible requirement for permanent monitoring stations for persistent violations.
Public comment: Shirley May (resident) asked whether the county had adopted A‑weighted dB targets; Presenter explained the frequency‑band approach is intended to be more protective and that the draft already set lower thresholds and nighttime levels for protected uses. The work group asked staff to draft clearer definitions and mitigation language for inaudible waves and to include pressure‑wave terminology.
What’s next: staff will add or refine vibration/pressure‑wave language, confirm remediation pathways, and include the acoustic modeling and monitoring requirements in materials for the APC update.
