Energy and Natural Resources

Regulators Tell Wind Farms to Quiet Down

17 November 2017

Quiet down!

That was the word from the Vermont Public Utility Commission to wind farm developers as it adopted a rule that sets standards for the sound produced by wind generation facilities.

The rule was mandated by legislation passed in 2016.

The new rule sets standards for three categories of wind facilities: small (up to 50 kW), medium (50 to 150 kW), and large (greater than 150 kW).

New rule for wind turbine noise levels. Credit: WikimediaNew rule for wind turbine noise levels. Credit: WikimediaFor the small and medium categories, the rule sets a 42-decibel limit 100 feet from nearby homes. That’s roughly on a par with noise levels in a library, according to Purdue University. For the large category, the limit is 42 decibels during the day and 39 decibels at night.

For comparison, 70 decibels is an arbitrarily set level above which sounds can be annoyingly loud. For example, Purdue says that a passenger car at 65 mph at 25 feet registers roughly 77 decibels (dB); a freeway at a distance of 50 feet from the pavement edge at 10 a.m. is roughly 76 dB; living room music is roughly 76 dB; and a vacuum cleaner is about 70 dB.

Under the new Vermont rule, project developers will be required to file information representing the expected sound levels at neighboring residences. Once constructed, large wind projects will be subject to sound monitoring to determine if they comply with the sound-level standards. Medium-sized projects may choose to conduct sound monitoring or construct their facilities a minimum distance from nearby homes.

For all projects, a neighboring landowner may agree that the limits in the rule do not apply to his or her property.

Under Act 174, the PUC was required to adopt a rule “regarding sound from wind generation facilities approved under 30 V.S.A. § 248.” The Commission was directed to consider: (1) standards that apply to all wind generation facilities, (2) a methodology for determining sound levels and measurement locations for each such facility on a case-by-case basis, or (3) standards that apply to one or more categories of wind generation facilities, with a methodology for determining sound levels and measurement locations for each wind facility on a case-by-case basis.

The adopted rule was to take effect on Nov. 22, 2017, and will apply to any facility that files for a certificate of public good on or after that date. The rule will not apply to any existing or pending wind generation facilities.

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