Two different acoustic studies near the Willow Creek Energy Center in eastern Oregon have found that the state’s wind farm noise ordinance is being violated at several homes nearby.  How often and by how much the violations are occurring remains under contention. As reported by the East Oregonian, the commission heard from several acousticians as well as the neighbors themselves.

The state allows wind farms to be up to 36dB at neighboring homes (10dB over the night-time ambient of 26dB–based on the assumption that excess noise will not be bothersome until it exceeds ambient by 10dB).  After several neighbors raised concerns about noise, Invenergy, the wind farm developer, hired acoustical consultant Michael Theriault to take measurements.  He found that noise levels at three homes were “usually less than 37db” and that at one home, “the noise ‘moderately’ exceeded the noise code about ten percent of the time.” (it is unclear what “usually” means in this report, or what averaging period was used in the determination)

However, the Theriault did no recordings when wind speeds exceeded 9m/s, because the company says their turbines don’t get louder after that point.  This may well be true, but sound propagation can vary widely with atmospheric conditions, especially when wind is higher aloft (at turbine hub height) than on the ground.  Acoustical consultants hired by the four landowners presented findings that included measurements when wind speeds were higher, which showed that the noise at the Eaton’s residence hovered just above the noise standard on a regular basis, and at the Williams residence it regularly went above 40 decibels. The wind farm consistently broke the noise rule at precisely the time when Theriault decided not to use the data – when wind speeds exceeded 9 meters per second. When the data is analyzed in a wider range of wind speeds,  the wind farm was in violation of the rule 22 out of 37 nights. “I’m not sure how someone can say this is an unusual, infrequent event,” said Kerrie Standlee. “To me, 59 percent is not occasional or unusual.” Standlee’s noise study also went beyond Theriault’s in that he gave the residents a sheet of paper to log their experiences with time and date. He then overlaid those comments on the data and showed that when the residents reported high noise, the wind was blowing from a particular direction or at a particular speed.

The commission also heard heartfelt testimony from the residents themselves, who said that their lives had been completely changed since the wind farm came. “A basic right in my life is to live in my beautiful home with my peace and quiet, and now I can’t do that,” Dan Williams said. When the testimony ended, the planning commission agreed to wait until their next meeting to make a decision about whether – and how – the Willow Creek wind farm must mitigate the noise problem.  An earlier article focusing on the experiences of people near the wind farm is available here.