Sound modeling expert testifies in Penn Forest wind turbine hearing

PENN FOREST TWP., Pa. - An expert in sound modeling testified at Tuesday evening's Penn Forest Township zoning hearing regarding an application for 28 wind turbines in the township.

Robert O'Neal, a principal at the Massachusetts-based environmental consulting firm Epsilon Associates, bolstered the sound modeling conducted by Atlantic Wind LLC, adding that he believes the turbines will be compliant with township restrictions that require them to be no louder than 45 decibels.

O'Neal testified that Atlantic Wind's sound modeling utilizes the industry standard metric for decibel levels. He added that the Leq metric used in Atlantic Wind's modeling is widely accepted for wind energy projects due to its ability to separate turbine noise from noise from other sources.

O’Neal testified that the Leq metric measures sound levels over a period of time, rather than spikes in sound. This metric is is used most often in measuring wind turbine sound, he said.

“The Leq is by far the most often used metric in the field of acoustics.”  O’Neal said. “It’s the most stable, reliable metric.”

His testimony contradicted that of Robert Rand, another acoustic expert who testified on behalf of objectors to the project back in July. Rand testified that Atlantic Wind’s sound models should have used a metric called Lmax, which measures the highest sound levels of a noise source.

O’Neal said the Lmax metric is better suited for “short duration events,” unlike the continuous nature of wind turbine operation. The Leq metric, he said, can measure the sound coming specifically from the turbine itself, whereas the Lmax metric picks up on all sounds. O’Neal suggested this improperly skews the real sound level of the turbine.

In July, Rand said that an Leq doesn’t take into account the spikes in sound that come from wind turbines. O’Neal disagreed with that line of thought, adding that the Leq is a “very conservative” metric that positively skews toward higher decibel levels.

Attorney Bruce Anders looked to discredit O’Neal’s insistence of the Leq metric during cross-examination, pointing to court rulings that favored the Lmax metric in municipalities with ordinances similar to Penn Forest Township.

Additionally, Anders referenced modeling conducted by O’Neal’s own colleagues that utilized the Lmax metric for sound modeling, despite O’Neal’s skepticism of the metric.

O’Neal believes that the turbines will comply with the township ordinance. He said that even if they exceed 45 decibels, there are options Atlantic Wind can take to reduce their decibel level, such as using low noise trailing edge blades. He also said control centers will continuously monitor the operation of each wind turbine if approved, which could allow them to adjust the sound of a turbine, if needed.

When questioned about the topic by Township Solicitor Thomas Nanovic, O’Neal noted that the control centers don’t measure the sound specifically, but measure operations that could impact the sound.

“Whatever they’re monitoring, they’re not monitoring the sound generated by the wind turbine,” Nanovic observed.

“No they’re not,” O’Neal said.

The next hearing will take place on Tuesday, Oct. 30 at the Penn Forest Township Fire Company #1.