How loud is a wind turbine?If you are on a country road, there is a light breeze and there are wind turbines two kilometres away, you will probably be just able to hear them. If there is a car traveling on the road within one or two kilometres you probably won't hear the turbines because of the noise from the car. If there is a strong breeze then you probably won't hear the turbines from a kilometre or more because of the noise the wind is making in nearby trees or shrubs. When I visited a wind farm during a strong gale I could not hear the turbines until I came within a couple of hundred metres.
Wind turbines are not loud in the sense that pneumatic drills and jet engines are loud. Sound levels from turbines are typically no more than about 55 dB (A) when measured at a distance of about 100 m; this is the same level of sound as you can expect from a car traveling at 60 km/h at the same distance.
Sound levels always decline with distance; the rate of decline (with some exceptions) follows the inverse-square-law – twice the distance a quarter the sound, three times the distance a ninth the sound, etc.
The level of background noise at distances of a kilometre or more from wind turbines makes measuring the effect of sound from wind turbines on people at such distances complicated.
From my own experience I cannot imagine how the sound from a wind turbine could keep anyone awake at night and a report by Health Canada (the government department that is involved in health in Canada) indicates that loss of sleep due to wind turbine noise is a negligible problem. A strong antipathy to wind turbines is linked with annoyance from the sound.
In Wind Turbine Noise, Infrasound and Noise Perception by Anthony L. Rogers, Ph.D., Renewable Energy Research Laboritory University of Massachusetts at Amherst USA, 2006/01/18, Rogers stated that as a rule of thumb, three times blade tip height from a turbine to a residence gives acceptable noise levels. I believe that this rule is used in Denmark, where there seem to be relatively few complaints about turbine noise and claims of health problems from turbines are practically unknown.
The Guardian carried an interesting
by Calla Wahlquist on 2015/06/26 about the local people's views on the
Collgar Wind Farm in
the Western Australian Wheatbelt.
Two of the local farmers said that, while the nearest turbine was only a
kilometre away, they could not hear it from inside the house and only
occasionally from outside.
"Modern large turbines have low sound levels at ground level. For example, in December 2006, a Texas jury denied a noise pollution suit against FPL Energy, after the company demonstrated that noise readings were not excessive. The highest reading was 44 decibels, which was characterized as about the same level as a 10 mile/hour (16 km/h) wind."The sound level perceived at distance from a turbine can depend on thermal layering in the air. A temperature inversion (a layer of cold air at low altitude, as often occurs at night) can cause sound to curve down toward the earth, resulting in the sound levels at a distance being higher than they would otherwise be.
Research by Stefan Oerlemans placed on the Net by the University of Twente looked into placing saw-teeth on the trailing edge of turbine blades to reduce sound levels.
The Acoustic Ecology Institute's "Wind Farm Noise 2011: Science and policy overview", compiled by Jim Cummings, makes the point that several Scandinavian studies have shown turbine noise annoyance is notably higher in rural settings than in more built up areas.
The South Australian Environmental Protection Agency (EPA) produced a report titled "Infrasound levels near windfarms and in other environments" in January 2013. Extracts from the Executive Summary:
The Association of Australian Acoustical Consultants produced a Position Statement on Wind Farms (available from their downloads page). Among other things it stated that "investigations conclude that infrasound levels adjacent to wind farms are below the threshold of perception and below currently accepted limits set for infrasound".
An Australian Senate Committee, looking into alleged health effects from wind turbines, concluded the following in November 2012:
"The committee concludes that, while it is possible that the human body may detect infrasound in several ways, there is no evidence to suggest that inaudible infrasound (either from wind turbines or other sources) is creating health problems. In contrast, there is an established literature confirming the existence of psychogenic, or nocebo, effects in general, and at least one study suggesting they may be responsible for symptoms in some wind turbine cases."
Infrasound from Wind Turbines – Fact, Fiction or Deception; Geoff Leventhall. Published in Canadian Acoustics, Vol. 34 No.2 (2006). I can't do justice to this paper here, but will include a couple of points.
In the abstract Leventhal wrote: "The perception of infrasound occcurs at levels higher than the levels produced by wind turbines and there is now agreement amongst acousticians that infrasound from wind turbines is not a problem."
Leventhal said that older down-wind turbines (those in which the blades are on the down-wind side of the tower) did sometimes cause vibrations in lightweight buildings nearby, but that "Modern up-wind turbines produce pulses which also analyse as infrasound, but at low levels, typically 50 to 70dB, well below the hearing threshold. Infrasound can be neglected in the assessment of the noise of modern wind turbines".Senate inquiry into the 'Social and economic impact of rural wind farms' (No. 353) he stated that:
"... the hearing and vestibular systems are subjected to very high levels of body generated noise. These include, walking, breathing, heartbeat, chewing and head movement. Body noises generated in this way were a problem in the Cochlear Ltd project to develop a fully implantable cochlear implant. In this case the microphone was implanted subcutaneously behind the ear. The level of infrasound picked up from the body by this microphone was a major problem and far exceeded all sound from external sources. In fact turning the head or chewing were some ten times louder than the external sounds we were trying to pick up.
presentation to a meeting of wind farm
opponents, the Waterloo Concerned Citizens Group.
The meeting was not advertised to the general public.
(Professor Doolan had earlier told me by email that he would keep me informed
on the progress of his research.
He has given me nothing and did not inform me about the meeting.)
For a scientist, attached to a major Australian university (Uni. of Adelaide), who one would hope was independent, unbiased and objective, to release his findings only to a group that is on one side of the controversy over wind farm noise, before publishing, and not giving supporters of wind power a chance to attend is questionable ethical behaviour. I have emailed Professor Doolan on this point (2013/02/06).
It seems that Professor Doolan did not make any very specific statements about the noise levels from the wind farm. He is reported as saying:
"further research would need to be undertaken to determine whether or not the noise experienced by residents was a result of the wind turbines, and to do this researchers would need the cooperation of the wind farm operator, Energy Australia."
Professor Doolan said that Energy Australia (EA) had declined to cooperate with his research. I put this to Steve Brown of EA and was told that the reasons for this were that "EA had problems with Doolan's methodology" and the cooperation that Doolan was wanting involved economic loss of production to the wind farm.
As of 2013/03/31 I had not received a response from Professor Doolan.
Wind turbine sounds might affect some people in the same way as does a neighbour's 'music'. Some sounds are more annoying than others and different people can react very differently to the same sounds. The perception and the attitude of the hearer are important. There is evidence that wind turbine noise annoys some people sufficiently to disturb their sleep, with consequent health effects. This may occur at distances of a kilometre or more, while others can sleep peacefully right under wind turbines.
Some sounds can be restful; most people would say that the sound of surf is pleasant. It seems that a sound that varies in a random way might be more easily tolerated than one that varies systematically; even traffic noise, though unpleasant, is tolerated by most people.
Restful soundsThe 'swoosh, swoosh, swoosh' of wind turbines is similar to the sound of surf. I find it pleasant and restful.
"Noise absolutely horrible"Mr Bill Quinn, who appealed against one of the South Australian Hallett wind farms was quoted in the Flinders News (Port Pirie, 2011/11/23) as saying that "The noise coming from Hallett #2 [wind farm] was absolutely horrible." He lives three kilometres from the wind farm, but his mother lives two kilometres from some of the turbines. Mr Quinn said "Some nights [his mother] has to turn the ceiling fan on to drown out the noise".
If the wind turbine noise could be drowned out by a ceiling fan, which in my experience are very quiet, it could not have been loud.
Erroneous readingsI have heard it claimed that sound levels of up to 100 dB have been measured 3 km from wind turbines. Such readings can only be explained as being due to someone not familiar with sound meters allowing the wind to blow over the microphone.
On 2013/07/19 I received an email from John Simpson, who, among other things, has been involved in technical sound recording for major movies. John wrote the following:
"I work in sound as a profession, and the comment by one person [Keith Taylor, above] on room nodes is very correct. I work in a sound proof room, even with 3 levels of sound proofing I will still hear a truck low end rumble from over 1.5 km away inside the room. Yet if I go outside the room it's hardly audible. This is because the sound proofing cuts out all frequencies above 100HZ it [is] very hard and expensive to get rid of lower frequencies. So all I hear in there is 100HZ and below making it very easy to hear these low freq sounds. Also you do get spots in a room where the freq is more predominant, so I can believe that a normally quite home that's over a KM away could have spots in the house where 100hz and below will seem quite loud, and [a] position change of just 1 meter in some rooms can go from no sound to quiet loud, especially as the surrounds in these places are normally quiet, as there is little other noise to drown out the turbine noise.
This factor seems to have received little attention in the discussions around wind turbine noise and annoyance. I suspect it deserves more.Cape Bridgewater and Hepburn there has been a problem with a 'screech' produced by a particular series of REpower wind turbine.
Pacific Hydro (Cape Bridgewater) and Hepburn Wind have been working with REpower to try and get the problem fixed. It seems that the noise comes from the yaw system of the turbine; that is the machinery that turns the whole head of the turbine into the wind. The sound only occurs when the turbine is yawing. It is most noticable when the wind is very light; less than 3 metres per second.
A wind power opponent has made a video clip of the sound on UTube. Note that while the sound as recorded in the video would be annoying, it is only a little above the level of background sounds.
The house involved is about 650m from a turbine. There are few houses in Australia that close to wind turbines. High pitched sounds such as this are attenuated quickly with increasing distance.
I find it interesting that while there have been many complaints from wind power opponents about how much noise wind turbines make, this is the only recording that I have come across of a sound that could be truly annoying.
|Threshold of hearing|
|Rural night-time background|
|Wind farm at 350m|
|Busy road at 5km|
|Car at 65km/hr at 100m|
|Busy general office|
|Truck at 50km/hr at 100m|
|Inside a typical shopping center or restauant *||
|Inside modern car at around 90km/hr *|
|Passenger cabin of jet aircraft *|
|Pneumatic drill at 7m|
|Jet aircraft at 250m|
|Threshold of pain|
It is not unusual for people to be annoyed by noise or other vibrations
and blame wind turbines, when some other source is the true cause.
Much publicity is given to claimed noise problems from wind farms, while far less is given to noise from industrial sources such as mining, earth moving operations and low-flying aircraft and people can jump to unjustified conclusions when annoyed by an unfamiliar noise.
I have only heard wind turbines from a distance as great as 2.5 or 3km in ideal conditions; when there was very little wind where I was listening, but sufficient wind where the turbines were on a ridge-top to power them. I found that if there was a car on a road within about 2km of me I could not hear the turbines because of the noise from the car.
I have visited many wind farms in Australia; all of those that were in SA and Victoria up to April 2009, and several in WA. No matter what the strength of the wind, one has no trouble conducting a normal conversation immediately beneath a modern utility scale wind turbine (for example, greater than 1 megawatt). The sound can vary from minute to minute, depending on the direction of the wind in particular; it seems that a greater level of noise can result from turbulence when air flows over a turbine blade at some angle other than the optimal.
I have camped overnight beneath the turbines of Starfish Hill (1.5 MW turbines), Clements Gap (2.1 MW turbines), Waterloo (3 MW turbines) and North Brown Hill (2.1 MW turbines) wind farms and had no problem at all getting a good night's sleep; I found the sound of the turbines, if anything, to be relaxing. (Also see A good night's sleep at Waterloo in the section 'People driven from their homes by wind turbines?') I recognise that this is subjective and that the experience of others may be different.
I visited Toora in late April 2008, staying in the caravan park at the foot
of the hill on which the
Toora Wind Farm
(1.75 MW turbines)
The turbines, the nearest of which was 850m away, were barely audible from
the caravan park and then only once in a while.
I have also slept in an unocupied house about 500m from the wind turbines at
On these occasions I could not hear the turbines indoors at all.
I have taken sound level readings at Clements Gap Wind Farm (2.1 MW turbines) on several occasions; I recorded a maximum of 54 or 55 dB(A) at a distance of around 100 m from a turbine and the same immediately beneath a turbine. The sound levels at distances of 300-500 m were in the 40s, and at one or two kilometres, while the turbines were audible, my meter did not register a reading (it has a minimum of 40 dB). On all these occasions the breeze varied between light and strong (only once, when there was such a strong wind that some of the turbines had cut out, did I measure sound levels greater than 55 dB 100m from a turbine, on this occasion the sound level varied between 60 and 80 dB).
The Hallett Hill Wind Farm (2.1 MW turbines) has been involved in controversy, some of which involved alleged noise problems. On a visit in May 2011, while all the turbines were turning, my sound meter did not register a reading (it starts at 40 dB) at any of five points on the public roads that go closest to the turbines. The turbines were inaudible to me at the township of Mount Bryan, at a distance of 3.8 km from the nearest turbines.
My impression is that the sound of turbines at 1000m would be less, less constant, and much less annoying than traffic noise anywhere in a large city. I'd prefer the sound of wind turbines at 1000m to the noise of a neighbour's kid riding a trail bike, or a quad bike being used to spray a neighbouring vineyard, or bird scaring guns in neighbouring vineyards; all sounds that I hear periodically and are small annoyances.
I am inclined to think that in a country like Australia, with no shortage of good sites for wind farming, no wind turbine should be built within one kilometre of a home without the informed consent of the owner. To build turbines less than one kilometre from a home would be to risk making the lives of the people in that home less pleasant. On the other hand, a distance of 2km, as has been adopted in NSW and Victoria, is quite unnecessary and would only be enforced by a government that is ignorant of the facts or biased against renewable energy. Ideally, the distance between turbines and houses should be set according to sound levels.
Claims of ill-health due to turbines are highly questionable and it is very difficult to see why wind turbine noise should be any different from other environmental noise such as that due to traffic or even wind in trees or wires.
I have been writing these pages since February 2004.
Since Ms Sarah Laurie started her
campaign trying to convince people that wind turbines
cause illness in 2010 there have been quite a
few people complaining of excessive noise from wind turbines in my region,
Mid-North South Australia.
(More than 40% of Australia's wind power is in SA and well over half of SA's
wind power is in this region.)
Curiously, no one has ever invited me to visit their house and hear the
noise for myself.
Some years ago Ms Sarah Laurie arranged with a person who lives about 3km from turbines and complained of excessive noise to 'phone me when the noise was particularly loud so that I could go and hear it. The telephone call never came.
Some people who are opposed to the Waterloo Wind Farm have claimed that the noise in the very small township of Waterloo is so bad that several houses have been abandoned. I have visited Waterloo at least eight times, have got out of my car and listened. I have never yet heard the turbines (3km from the town) from the town, even though on several of those occasions the conditions were excellet, with no wind in the town, but a good breeze on the ridge and the turbines operating.
I find it difficult to conclude from this anything other than that the noise cannot really be as bad as these people claim it to be.
These claims are so contrary to my personal experience with the sound levels
from wind farms that I find it very difficult to understand how the people
involved can be so badly mistaken.
I accept that these people believe what they have said to be true, but I
cannot understand it except to put it down to a gross form of self-deception.
That humans can deceive themselves to this extent has been an eye-opener to
PharmacistGeorge Papadopolous of Yass has claimed that 40 wind turbines "35km away at times has turned the quiet rural area of the northern hills of Yass into a rumbling mess." I have corresponded with George several times. He seems quite convinced that he is right, I accept that he probably believes what he says to be true, even though it does not stand up to any sort of reasonable examination.
FarmerA farmer who lives about three kilometres from the Hallett Hill Wind Farm complained about loud noise at times. Ms Sarah Laurie arranged with him to inform me when the sound was particularly loud so that I could go and hear it. The phone call never came.
Interestingly, Anita Butcher who also lives about three kilometres from the same wind farm spoke of her take on wind power in a Youth of the Year Quest speech in 2013. In contrast to the above farmer, Ms Butcher said "I have not personally experienced any sound disturbances".
"... but I had the misfortune to get a flat tyre one day about two and a half kilometres from out in front of one of these whole rows of turbines. When I got out to change the tyre I could hardly hear myself think. It was just horrendous."
While I've visited almost all the wind farms in South Australia and Victoria and a number in Western Australia I have never come across loud sound at any distance at all; not even right underneath wind turbines.
Following a number of attempts to contact him, by telephone, email, and post, Mayor Mattey 'phoned me on 2013/10/29. After discussing the matter with him I accept that he was speaking in good faith in as much as he believed what he said to be true. He gave me clear directions to the location of the road, but was less clear on the exact place he had the flat tyre. He said in his submission, "I was on a bit of high ground out in front of the turbines, not as high as they were, but on high ground." He did not know the name of the road, but from his description it was Parker Road.
My wife and I visited the place on 2013/11/03. We parked our car at South Latitude 33.4197°, East Longitude 138.7406°, which seemed likely to be about where Mayor Mattey had his flat tyre, and walked one and a half kilometres along the road toward the row of wind turbines on the Brown Hill Range, finishing at Latitude 33.4205°, Longitude 138.7249°, at a point on the ridge on the line of the turbines. There was a moderate breeze and the wind turbines were operating.
Where we parked the car we could hear the turbines; I would describe the sound level as a bit more than barely audible. As we approached the line of turbines the sound level increased until on the ridge I recorded around 60dB, a level at which the turbines were plainly audible, but far from unpleasantly loud. As would reasonably be expected, the sound had steadily increased as we approached the line of turbines.
We did not experience anything remotely like what Mayor Mattey had described. What he heard is a complete mystery to me. It could not have been the wind in nearby trees or shrubs, the area is completely devoid of vegetation other than grasses etcetera.
The 2km setbacks from homes favoured by the Liberal Party in South Australia and Victoria (and the 5km from towns legislated in Victoria) is obviously very much out of step with international norms. This is, however, in line with the Australian Liberal Party's favouring of coal ahead of renewables. Here again, the Liberals are very out of step with the rest of the world.
The South Australian Environmental Protection Agency (EPA)
produced a report titled "Infrasound levels near windfarms and in other
environments" in January 2013.
A significant conclusion of the research was given in the 'Summary of
"This study concludes that the level of infrasound at houses near the wind turbines assessed is no greater than that experienced in other urban and rural environments, and that the contribution of wind turbines to the measured infrasound levels is insignificant in comparison with the background level of infrasound in the environment."While this research was not conducted at Waterloo, it is very relevant to the allegations that have been made about this wind farm. EPA site.
Because of the significant controversy around the Waterloo Wind Farm I will copy the summary of the findings of the EPA study here:
Health Canada, November 2014;
Wind Turbine Noise and Health Study:
Summary of Results – health and quality of life were found to be
unaffected by nearby wind turbines, some annoyance was found.
With particular regard to the present subject, Health Canada reported that:
"The following were not found to be associated with WTN exposure:In other words, there was no link found between sleep disorders and actual levels of wind turbine noise.
Unfortunately I cannot give more details because of the confidentiality of the complainants.
Similarly, health complaints have been made about mobile telephone towers before they were operating.
The blade tip height of the turbines used at Bluff Range is 124m. From the rule of thumb given by Dr Rogers (above), it would follow that sound levels would be acceptable at a distance of 372m (3 times blade tip height) from a single turbine. At 3.6km the sound pressure would be about a hundred times less (by the inverse square law of physics).
What is acceptable to some people is not acceptable to others!
|Anita Butcher lives in Mount Bryan 3km from the Hallett Hill Wind Farm and was a competitor for Youth of the Year in early 2013. As a part of the selection process for Youth of the Year competitors gave a speech on a subject of their own choice. Ms Butcher chose wind farms. She said: "I can honestly say that I have hardly heard a noise coming from the wind turbines."|
To be fully acceptable to scientists research generally has to be published in
reputable peer-reviewed journals.
Other links relating to wind power:
First hand experience
Health Canada's report
Geoff Leventhall on infrasound
Peter Seligman on infrasound
Mayor Peter Mattey, Goyder Council
Noise complaints when wind turbines were not operating
Noise; my own experience
Research on infrasound by Con Doolan
SA EPA research
Setbacks between turbines and homes
Sleep and wind turbines
Some noise claims
Some noise levels compared