A world-first Australian study has found that pulsing wind farm noise is sometimes audible inside a home up to 3.5 kilometres from a turbine, in findings likely to buoy those opposed to the low-emissions technology.
The Flinders University research gathered data at nine homes near a single, older-style wind farm in South Australia and did not study year-round conditions.
However the researchers say their findings demonstrate the need for further investigation into the potential relationship between wind turbine noise and sleep disturbance.
The Australian Wind Alliance said no wind farm noise complaints were lodged in South Australia last year and that the industry was widely accepted by rural communities.
Growth in large-scale renewables including wind farms has created thousands of jobs and helped drive down greenhouse gas pollution from Australia's energy sector.
Some people believe the low-frequency sound of wind turbines causes health issues for nearby residents. Previous studies have found no conclusive evidence of this.
However the first results from ongoing Flinders University research into turbine noise and sleep found that low-frequency pulsing from a South Australian wind farm was audible about 16 per cent of the time inside homes up to 3.5 kilometres from a turbine, including 22 per cent of the time at night. The noise was audible 24 per cent of the time outside the homes.
At night, audible pulsing occurred for as much as 22 per cent of the time, the data showed.
Recordings detected what complainants commonly describe as a pulsating, thumping or rumbling sound. The noise is technically known as amplitude modulation, and relates to a change in noise level that occurs approximately once per second as the turbine blade rotates.
Field data was recorded at nine homes within 8.8 kilometres of the wind farm. Microphones were placed inside and outside homes and recorded almost 18,000 10-minute samples between 2012 and 2015. The data was recently analysed and the results published online last month in the Journal of Sound and Vibration.
Audible pulsing decreased with distance from the wind farm. Between 7.6 kilometres and 8.8 kilometres from a turbine, audible sound was recorded only once during the study period.
No data was recorded at homes between 3.5 kilometres and 7.6 kilometres from a turbine.
The report's authors, led by research fellow Kristy Hansen, said the findings "have important implications for possible sleep disruption" from wind farms, particularly in quiet rural areas, and further work was warranted.
More research was also needed to determine the year-round prevalence of audible wind turbine pulsing, as well as to quantify the extent to which people find the noise annoying, the report said.
Dr Hansen said it was well known that amplitude modulation, or pulsing, "results in increased annoyance in listening tests" and was cited in complaints from residents living near wind farms.
Another recent study by the researchers found that wind farm vibration was unlikely to cause problems inside homes located more than 2.4 kilometres from wind farms.
In 2016 the research team was awarded a $1.4 million National Health and Medical Research Council grant for a wind farm noise study including lab tests and sleep measurement.
The call-out for the grant, and another for almost $2 million for wind farm studies by the University of NSW, came after then Prime Minister Tony Abbott in 2015 described wind farms as "awful and noisy" and then Treasurer Joe Hockey derided them as "utterly offensive".
Flinders University sleep and respiratory physiologist Peter Catcheside, who is heading the NHMRC research, said his team had unsuccessfully approached four South Australian wind farm operators to request data to aid their studies.
"Unfortunately they have either not responded or declined with concerns about commercial sensitivity issues," he said.
Professor Catcheside said questions around the relationship between wind farm noise and sleep disturbance could be better answered if the field measurements could be correlated with industry data on wind speed and direction.
Australian Wind Alliance national co-ordinator Andrew Bray said wind farms were "a clean and safe way of generating electricity and this report hasn't found anything to challenge this".
"The report is very limited and only studies a single South Australian wind farm, using older technology, from around five years ago," he said.
"The National Wind Farm Commissioner received not a single complaint about wind farm noise in South Australia last year, suggesting that the noise features studied in this report are not an ongoing issue."
Mr Bray said wind farms were a well-established part of many rural landscapes and were generally widely accepted.
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