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Wind farms have noise detectives on the prowl  

Credit:  Richard Blackwell, The Globe and Mail, www.theglobeandmail.com 23 August 2010 ~~

A Toronto company hired by the Ontario government is probing for the ‘cold hard facts’ about health problems caused by the sounds emitted from wind turbines

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 Engineering Ltd., a 30-employee acoustical consulting firm, created the rich sounds of some of the classiest theatres in Canada – the new Four Seasons opera house and the Royal Conservatory of Music concert hall in Toronto, and Vancouver’s Queen Elizabeth Theatre, among many others.

Now 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 vibration 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.

Aercoustics already has some experience with wind projects – it helped investigate complaints about noise coming off wind turbines at the Kingsbridge wind farm built by Epcor Utilities Inc. on the shores of Lake Huron. The company’s measurements pinpointed the issue as a malfunctioning gearbox on some of the turbines, and Epcor was able to fix the problem.

Mr. O’Keefe noted that in the 1950s and 1960s, designers thought they had figured out exactly how to create perfect concert hall acoustics, but many of those venues ended up with poor-quality sound. Much more has been learned since then about concert acoustics, and that technology has vastly improved newer facilities.

“It could be the same thing here [with turbines noise],” he said, with new technology giving a better picture of exactly how sound is emitted. “We have to keep an objective, open mind.”

***

WHIRLING CONTROVERSY

The debate about the potential health impacts from wind turbines is intensifying as thousands of the huge structures pop up across Canada.

Critics of the industry cite dozens of reported cases around the globe where people living near wind farms say they have suffered headaches, sleep deprivation and other illnesses as a result of the audible noise, low frequency vibrations, and visual flicker from turbines.

But several reports from government agencies worldwide, including one last spring from Ontario’s chief medical officer of health, say there is no direct link between wind turbine noise and the health of people living nearby.

The wind industry, too, insists there are no risks. Last year, the Canadian Wind Energy Association, along with its sister organization in the United States, released a paper authored by a panel of scientists who concluded that there are no direct physiological effects on people living near turbines.

Some of these reports do acknowledge, however, that turbine noise may annoy people living nearby, causing stress and disturbed sleep.

Wind energy critics, including the Canadian-based Society for Wind Vigilance, say more research is needed, including independent health studies to analyze the effects of turbine sounds and vibrations. They say that without common standards in place to measure turbine noise, it is premature to declare the problem non-existent.

Richard Blackwell

***

ACOUSTIC ADVANCES

Aercoustics Engineering Ltd. principal John O’Keefe says one of the key advances in acoustics in recent decades has been the recognition that experiencing sound is multidimensional.

Just as a restaurant outing involves more than just the taste of the food (ambience and service are also crucial), the experience of sound includes multiple dimensions, he said.

Acoustical engineers designing concert halls in the past focused almost exclusively on reverberation time – how long it takes the sound from the music to decay. In recent decades, they’ve realized that other factors such as clarity (the ability to differentiate sounds), lateral energy (sound from the side) and loudness are also important.

At the same time, the technology for measuring, analyzing and modelling sound improved dramatically, Mr. O’Keefe said. “Suddenly, with the power of a desktop you could build a computer model of a concert hall and you didn’t need a mainframe.”

Among Aercoustics’ current clients is Imax Corp., the big-screen movie company that is planning to build a series of portable, inflatable theatres for special events or in non-traditional markets. Aercoustics is helping Imax understand the acoustics of the innovative structures, which seat about 450 people.

“No one ever really cared about the acoustics of a plastic building before, Mr. O’Keefe said. While the acoustics of wood, drywall and fibreglass are well understood, he said, it is a challenge to figure out how sound bounces around inside what is essentially a large plastic bubble.

Richard Blackwell

Source:  Richard Blackwell, The Globe and Mail, www.theglobeandmail.com 23 August 2010

This article is the work of the source indicated. Any opinions expressed in it are not necessarily those of National Wind Watch.

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