Sound already exceeds these values at a given location and time, subsection B governs at that location. In all other circumstances the more restrictive of this subsection or subsection B governs.

Infrasound. Infrasound (1 Hz to 20 Hz) shall not exceed sixty-five (65) dB(Z) at any Property Line, measured per ANSI S2.7 with instrumentation appropriate to infrasound; microphone-only measurement is not valid. Operations shall not generate vibration, oscillation, or infrasound causing perceptible resonance within any building or adverse effects on the human body, determined per ISO 2631 and ANSI standards for human exposure.

Tonal Penalty. Every sound study shall include narrow-band analysis per ISO/TS 20065. For sound above 20 Hz, where the decisive audibility of any narrow-band averaged spectrum is 10 dB or more, a 6 dB penalty shall be added to the measured A-weighted level for compliance purposes.

Vibration. Ground-borne vibration attributable to the facility shall not exceed a peak particle velocity of [0.02] inches per second at any Property Line, and shall not be perceptible without instruments at any Property Line.

Measurement. Measurements shall use sound level meters per ANSI S1.4 and Class 1/Type 1 instrumentation per IEC 61672-1 with one-third-octave capability per ANSI S12.9, at microphone heights of four (4) to five (5) feet, under suitable meteorological conditions (no precipitation; sustained wind at the microphone not exceeding 12 mph), at monitoring locations shown on the site plan at the points most susceptible to noise. Compliance is evaluated cumulatively for the facility, not source-by-source. Infrasound shall be measured in accordance with subsection (D).

Outages; Testing. The limits of this Section apply at all times, including during outages, Emergencies, equipment failures, testing, and maintenance. No allowance above subsections (B) and (C) is available, and the more protective standard governs.

Verification and Enforcement. Post-construction compliance testing of all levels, including infrasound, using the baseline methodology, shall occur within three (3) months of commencement of operation. The County may test at any time. Continuous monitoring shall stream to the Public Dashboard under Article XI, and third-party daytime and nighttime noise reports shall be filed publicly each year. Upon any verified exceedance, the automatic curtailment of Article XI applies; a sustained exceedance allows a cure period not exceeding one (1) month, after which the County may revoke the Conditional Use Permit and operations shall cease until compliance is demonstrated.