It’s midnight on Shawmut Street, and the southwesterly wind makes the location “an optimal spot for sound testing” Fairhaven’s turbines, said Laurel Carlson, a technician with the state Department of Environmental Protection.

In front of her is a sound meter. Roughly 7 inches long, it’s shaped like an oar, with a foam ball at the skinny end protecting the microphone that points diagonally up toward the turbines. The meter’s buttons glow in the dark. It sits on a tripod on the lawn overlooking the wetlands that reflect the light of the full moon.

Above the marsh, turbine blades spin, glowing orange from lights on the nearby radio tower.

On the ground, the wind is blowing 2.3 meters per second. At the hub of the turbines, it blows 6.5 meters per second.

“Three, two, one, go,” Carlson says, and the sound sample begins.

With her is Fairhaven Wind Developer Sumul Shah, who watches a graph on his laptop showing the turbines’ power output. The computer records second-by-second data for wind speed and power output that will be compared with the noise data later.

Both Shah and Carlson are wearing headlamps, and her light bobs up and down as she looks from the meter to her clipboard, where she writes down the decibel levels.

Every five seconds over the course of five minutes, she records the numbers: 47.8, 46.6, 47.7, etc.

The whooshing of the turbine blades is distinctly audible over the breeze and the crickets. Every so often, Carlson shakes her head, and writes the letters “G” or “C” to show when gusts of wind or car noises interfere with decibel readings.

“Well, we had some interesting noises on that one,” she says after five minutes have passed.

Early morning Friday was the second round of testing Carlson has conducted on Fairhaven’s two wind turbines. Her goal is to assess whether the noise made by the turbines is 10 decibels louder than Fairhaven’s ambient sound, which would put them in violation of Massachusetts’ noise regulations.

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