December 20, 2011

Thousands at risk of turbine hum

The Sunday Times, 18 December 2011

Thousands of people living near wind turbines could find their lives blighted by the noise, researchers have warned.

Acoustic scientists estimate up to a fifth of Britain’s wind farms generate a low- frequency hum that can be audible for more than a mile.

With the government planning a huge expansion of wind turbines, some experts want the limits on wind turbine noise – 35 decibels during the day and 43 decibels at night, the equivalent of a buzzing fridge – to be lowered.

The impact of the pulsating sound, a phenomenon called “amplitude modulation” (AM) which is believed to be caused by the turbine blades striking patches of turbulent air, has already led to payouts from energy companies.

Earlier this year, Jane and Julian Davis took a wind farm operator to court, claiming that the noise from nearby turbines had forced them from their Lincolnshire home. They settled for an undisclosed sum.

John Huxtable, 64, has been unable to open the windows of his bungalow in Putford, north Devon, since a 360ft turbine 500 yards away was switched on this year. “The noise is absolutely horrendous.
It’s worst in the evenings when everything else is quiet,” he said.

Rules governing the noise created by wind turbines are based on continuous background noise and do not take into account the bursts of loud noise also associated with AM.

Mike Stigwood, a noise consultant, estimates that 20% of wind farms suffer from AM, which, he believes, is caused by differences in wind speed and turbulence at the top and bottom of the blades as they spin. Walls and roofs tend to filter out higher-frequency sounds but allow deeper noises such as AM to penetrate.

Dr Lee Moroney, planning director at the Renewable Energy Foundation, a charity that has called for tougher regulations, said: “Noise of this kind disrupts sleep and so can have a devastating effect on people’s lives. The solution is greater separation distances between turbines and dwellings.”;

RenewableUK, the industry body, said a review of AM was under way, adding: “We think that the regulations are robust enough . . . Once the research into AM is finished, we will look into ways we can minimise it.”

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