By Graham Lloyd, Environment Editor, Sydney
The study by acoustics expert Steven Cooper is the first in the world in which a wind turbine operator had fully co-operated and turned wind turbines off completely during the testing.
It opens the way for a full-scale medical trail that may resolve the contentious debate about the health impact of wind farms.
Funded by wind farm operator Pacific Hydro, the study was conducted at Cape Bridgewater in southwest Victoria where residents have long complained about headaches, chest pains and sleep loss but have been told it was all in their minds.
As part of the study, residents living between 650m and 1.6km of the wind turbines were asked to diarise what they were experiencing, including headaches, pressure in the head, ears or chest, ringing in the ears, heart racing or a sensation of heaviness.
Their observations were separated into noise, vibration and sensation using a one to five severity scale.
“The resident observations and identification of sensation indicates that the major source of complaint from the operation of the turbines would appear to be related to sensation rather than noise or vibration,” the report says. “For some residents experiencing adverse sensation effects, the impact can be exacerbated by bending over rather than standing, with the effect in some cases being reported as extremely severe and lasting a few hours.”
Mr Cooper said it was the first time that sensation rather than audible noise had been used as an indicator of residents’ perception of nearby wind turbines.
The report found offending sound pressure was present at four distinct phases of turbine operation: starting, maximum power and changing load by more than 20 per cent either up or down.
Mr Cooper said the findings were consistent with research into health impacts from early model wind turbines conducted in the US more than 20 years ago.
The relationship between turbine operation and sensation demonstrated a “cause and effect”, something Pacific Hydro was not prepared to concede, he said.
Survey participant Sonja Crisp, 75, said the first time she experience discomfort from the wind turbines, “it was like a thump in the middle of the chest.
“It is an absolute relief, like an epiphany to have him (Mr Cooper) say I was not crazy (that) when I am doing the dishes I feel nausea and have to get out of the house.”
David Brooks, from Gullen Range near Goulburn, NSW, said health concerns from wind farm developments were not confined to Cape Bridgewater.
The findings should be used as the basis for a thorough health study of the impacts from low frequency noise, he said. “Until this is done, there should be a moratorium on further wind farm developments,” he said.
Pacific Hydro and Mr Cooper agree that more widespread testing is needed. Andrew Richards, executive manager external affairs at Pacific Hydro, said: “While we acknowledge the preliminary findings of this report, what they mean at this time is largely unclear.
“In our view, the results presented in the report do not demonstrate a correlation that leads to the conclusion that there is a causal link between the existence of infrasound frequencies and the ‘sensations’ experienced by the residents.” Mr Cooper said the findings had totally discounted the so-called “nocebo” effect put forward by some public health officials, who said symptoms were the result of concerns about the possibility of experiencing them.
The Cape Bridgewater study included six residents over eight weeks in three houses.
One hearing-impaired participant had been able to identify with 100 per cent accuracy the performance of wind turbines despite not being able to see them.
Another Cape Bridgewater resident Jo Kermond said the findings had been “both disturbing and confirmation of the level of severity we were and are enduring while being ridiculed by our own community and society.”
Mr Cooper said residents’ threshold of sensations were experienced at narrow band sound pressure levels of four to five hertz at above 50 decibels.
The nominal audible threshold for frequencies of four to five hertz is more than 100 decibels. Mr Cooper said an earlier investigation into health impacts of wind farms by the South Australian EPA had been flawed by limiting the study to only one-third octave bands and not looking at narrow band analysis.
“By looking at high sensation and narrow band I have developed a methodology to undertake assessments using narrow band infrasound,” he said.
“We now have a basis on how to start the medical studies,”
Mr Cooper was not engaged to establish whether there was a link between wind turbine operation and health impacts, “but the findings of my work show there is something there,” he said.
Mr Cooper said Pacific Hydro should be commended for allowing the work to proceed.
“It is the first time ever in the world that a wind farm has co-operated with a study including shutting down its operations completely,” he said.
Mr Cooper has coined the term Wind Turbine Signature as the basis of the narrow band infrasound components that are evident in other studies. He said the work at Cape Bridgewater had established a methodology that could be repeated very easily all over the world.
Pacific Hydro said it had conducted the study to see whether it could establish any link between certain wind conditions or sound levels at Cape Bridgewater and the concerns of the individuals involved in the study.
“Steven Cooper shows in his report, for the limited data set, that there is a trend line between discrete infrasound components of the blade pass frequency (and harmonics of the blade pass frequency) and the residents’ sensation observations, based on his narrow band analysis of the results,” Pacific Hydro said.
“However, we do not believe the data as it currently stands supports such a strong conclusion.”
The report has been sent to a range of stakeholders, including government departments, members of parliament, environmental organisations and health bodies.
Cape Bridgewater Wind Farm