Rehashing sound studies

Over the weekend, Cape Vincent officials spent about 10 hours working on their wind turbine zoning law. They had a briefing on sound with William J. Elliot, senior consultant for Cavanaugh Tocci Associates, Sudbury, Mass., on Friday, followed by hashing out sound and setback requirements in the law on Saturday.

Like his boss, Gregory C. Tocci, Mr. Elliot talked about the sound study conducted by Hessler Associates Inc., Haymarket, Va. Almost a year ago, Mr. Tocci told Clayton’s wind committee that the sound analysis connecting wind speed to turbine noise was inappropriate because of the method of sampling and the loose correlation between the data.

Mr. Elliot conveyed the same information on Friday. In Cape Vincent, Hessler had four sound monitoring stations and their measurements were compared with wind speed data collected at a different site at different heights. Hessler then picked a wind speed of 6 meters/second, when a turbine would be spinning, to find an average background sound level. The average of the data points at that speed was 37 decibels.

In evaluating the study, Cavanaugh Tocci eliminated the wind speed data and just looked at the sound levels, which showed a background noise level of 25 decibels.

For reference, a difference of 10 decibels represents a doubling or halving of sound as perceived by humans.