http://www.theglobeandmail.com/report on business/industry news/energy and resources/article1681893.ece
Wind farms have noise detectives on the prowl (excerpts)
By Richard Blackwell
A small Toronto company that designed the acoustics of many of Canada’s premier concert halls is now figuring out the best way to measure noise from wind turbines, a project that will have major implications for the country’s burgeoning wind power industry. Aercoustics has won a contract from the Ontario government to develop techniques for measuring the audible noise from wind turbines, and will deliver the results to the province this fall. There is no accepted procedure anywhere for measuring noise from turbines, Ontario officials say, so Aercoustics’ report could help set standards across the country and internationally.
But the company is wading into what has become a controversial issue as wind farms sprout across Ontario and the rest of the country. While Ontario long ago set guidelines for the amount of noise turbines are allowed to emit, it has never had a consistent, formal method of measuring that noise. That has infuriated wind farm opponents. “These wind developments that are now in existence have gone forward without this kind of knowledge,” said Beth Harrington, a spokeswoman for the Society for Wind Vigilance. “It’s one of those cases of the cart before the horse.”
Critics say the noise and vibrations from turbines can cause a variety of health problems—including stress and sleep deprivation—for those who live nearby. With more than 2,000 turbines already built across Canada and thousands more planned, increasing numbers of people will be exposed to the noise. Many wind developers dismiss worries about turbines’ possible effect on health, saying there is no evidence of such a link.
Aercoustics’ executives are careful not to take sides in the debate. “[We’re] coming at it from an engineering point of view, [so] it’s got to be objective,” said John O’Keefe, a principal of Aercoustics and one of the company’s five shareholders. The idea is to be able to determine “cold hard facts, measured consistently.”
In addition to its work with concert halls, Aercoustics has established itself as an innovator in industrial and environmental work. It designed a rubber isolation system that keeps residents of a condo building constructed directly over Toronto’s Bloor subway line from feeling any vibra-tion from the trains below. And it has helped companies ranging from ethanol producers to gravel quarries mitigate their sound problems.
Mr. O’Keefe noted that just because no one has yet made a convincing scientific case for the link between turbine noise and health, that doesn’t mean one doesn’t exist. “What we have to do as engineers is to keep an open mind,” Mr. O’Keefe said.
Essentially, Aercoustics will recommend to the government how best to measure turbine sounds: what kind of measuring equipment to use, where to place the sensors and at what height, and how to filter out the buffeting from the wind. Mr. O’Keefe said the techniques will allow a consistent “apples to apples” comparison of wind turbine noise at different sites, so the government can see if developers are complying with the rules and investigate noise complaints.
One key issue, said Aercoustics principal Vince Gambino, is to differentiate the sound of a turbine from the background noise of the wind. “There’s some difficulty in sorting out what component of the sound is from the wind and what component is from the turbine itself,” he said. Aercoustics is developing sophisticated analysis software that can help sort that out. Most complaints about turbine noise come when wind speeds are low to moderate—below about 25 kilometres an hour, Mr. Gambino said. As wind speeds increase, turbines move faster and produce more noise, but that noise is partly masked by the wind.