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Senate Select Committee on Wind Turbines - 23/06/2015

SWINBANKS, Dr Malcolm Alexander, Private capacity

Committee met at 17:05

Evidence was taken via teleconference—

CHAIR ( Senator Madigan ): I declare this meeting open and welcome Dr Malcolm Swinbanks. Information on parliamentary privilege and the protection of witnesses has been provided to you, has it?

Dr Swinbanks : Actually it has not. It was not in amongst the emails that I got. Perhaps you could quickly indicate.

CHAIR: The committee has your submission. I now invite you to make a short opening statement, and at the conclusion of your remarks I will invite members of the committee to put questions to you.

Dr Swinbanks : Just briefly, I will review the submission that I made. I addressed four separate issues: first of all, the physical mechanisms for generating low-frequency sound and infrasound; secondly, the mechanisms by which people can perceive such infrasound; thirdly, I commented on the health effects and, in particular, two reports relating to these supposed health effects or the absence of them; and, finally, I gave an account of my own personal experience of adverse effects I have encountered when taking measurements near to a wind turbine installation.

If I could start off with the generation of infrasound, it is not often realised that NASA, in the early 1980s, actually carried out research on upwind rotor turbines. That is the modern configuration where the rotor is upwind of the supporting the tower, rather than downwind. Wind developers have often dismissed NASA's work, saying it was not relevant because it related only to downwind turbines, but this is completely inaccurate. NASA had in fact identified the benefits of going to the upwind configuration at a very early stage. They also examined the effects of multiple turbines operating together and the effects of the separation between those turbines. They found that seven to 10 diameters separation was the ideal requirement for a turbine located downwind of its neighbours. But, in recent years, some wind developers have compromised on that spacing and have reduced it even to as little as three diameters in some cases, and that is asking for trouble, because the increased turbulence leads to increased low-frequency sound and infrasound.

The other effect that has to be considered is that as wind farm arrays are made larger and larger, the rate of attenuation as you move away from the wind farm is reduced. The result is that the setbacks from the boundaries have to be much greater to achieve the same reduction in sound. In recent years, people have stated that they have problems at distances of as much as three miles, and that is entirely consistent with the effects of increasing the size of the wind farms. Finally, I would point out that under conditions where the temperature profile is what is known as a temperature inversion, the low-frequency noise and what would I call the 'silent thump' of wind farms can carry over distances of three miles or more.

I would like to turn to how people perceive infrasound. The conventional method of hearing is through what are known as the inner hair cells of the cochlear. The effects of infrasound can be measured by a G-weighting scale, which is very similar to the A-weighting scale. It is effectively an extension of it, although the exact values do not correspond directly. Many people have evaluated whether or not the effects of infrasound are perceptible by simply comparing spectra with the hearing threshold and stating that the spectra are well below the threshold values and therefore the sound cannot possibly be perceived. That is not correct. At very low frequencies, it is the combination of different frequency components adding together which defines the total level of the infrasound, and that can be significantly greater than is observed simply by looking at the par spectrum.

People have reported having significant problems believed to be due to infrasound at distances from wind turbines. In that context, there are three different mechanisms which may be contributing to enhanced sensitivity. I have analysed a specific effect relating to the interaction with the thresholds as a result of low and high frequencies being present simultaneously. In America, Dr Alec Salt has identified that the outer hair cells of the cochlear are actually much more sensitive at very low frequencies. He believes that there is some input to the nervous system resulting from them. Most recently, Paul Schomer, also in America, has considered the possible effects of sound pressure on the vestibular organs, which are the balance organs, and those effects could give the person on the receiving end a sensation of apparent motion, even though they are actually stationary.

I would like to make a further addition, which is just related to my own experience. Lying in bed, at a distance of three miles from a wind farm, my wife and I have on occasions been disturbed by the wind turbine noise. The most marked feature is that when you have gusts of wind, the turbine noise is masked by the gust and you get a huge sense of relief, only to find that when the wind subsides, the turbine noise returns and you again find yourself subject to the relentless sound.

The point is that when the wind gusts rise it is very much like the effect of when you come out of a tunnel into the light—a huge sense of relief. The sound levels of the turbines under those circumstances are probably less than the average sound levels of the wind, but nevertheless they are far more disturbing. This is noted also at higher frequencies, where people have identified that the annoyance from turbines at 35 dB(a) can be comparable to the annoyance of other more conventional sources at 55 dB(a). One commonly sees statements made that wind turbine noise is no different from any other noise, but the fact is it is different. It is clearly more perceptible at lower levels, and criteria relating to more conventional noise do not necessarily apply.

Turning to the health effects of wind turbines, there was an early report in 2009, which was an American Wind Energy Association funded report. This was the first time that experts had been brought together from both the medical profession and the acoustics profession. That report has been regarded as a definitive baseline report, and subsequent reports have tended to draw on it because of the qualifications of its authors. I consider that report to have been extremely biased. It failed to mention at all two of the most important aspects of wind turbine perception. Firstly, that in rural areas the hearing threshold is much reduced compared to the threshold when you are in urban areas and consequently you are much more sensitive to additional noise. Secondly, there is increasing sensitivity with continuing exposure. Some authors have described this a learned aversion. I have also experienced that at firsthand myself 30 years ago when working on natural gas compressor installations, which are effectively jet engines driving a compressor into an exhaust. In those circumstances, I found that over time, ultimately a period of two years, I had become very sensitive indeed to the low frequency noise and I could detect it under circumstances where previously I could not detect it at all.

That same health report misrepresented guidance which had been given in America by the Environmental Protection Agency as long ago as 1974—that is 40 years ago—and they have failed to indicate that the presently permitted sound levels in the USA are too high and can lead to sleep disruption. The most recent health report that has been produced, again, funded by CanWEA, the Canadian Wind Energy Association, finally acknowledges the excessive permitted levels in the United States and the resultant consequences for sleep disturbance, but it does not highlight this. The statement is effectively buried in 25 pages of closely-spaced text. Now I believe a lot of the problems have been created as a result of that report and some of its successors, because it has completely understated the nature of the problem and has led, undoubtedly, to people being exposed to higher levels than they should be exposed to.

At the same time, it is common practice to place the burden of the effects of wind turbines onto the homeowners by stating that it is annoyance on the part of the homeowners and nocebo effects. By placing the burden on the homeowners, the apparent responsibility of the wind developer is reduced but, at the same time, this ignores completely the fact that the noise and, indeed, the infrasound can represent a significant intrusion into a rural home, particularly at night when people are trying to sleep. So I believe the correct terminology is to say that people suffer annoyance. It is something which is imposed on them.

I would also comment with respect to the nocebo effect that many communities welcomed wind turbines—this was particularly true of one island community in Vermont—but once the turbines started they discovered that there were some significant adverse effects. That is the very opposite of a nocebo effect. A nocebo effect is when there is prior anticipation of a problem, not when the problem is noted after the event. In that sense, I would like to make a brief comment that NASA, as long ago as 1982, presented a curve which showed the levels of infrasound that could cause adverse reactions by occupants. This showed that the levels of infrasound could be very much lower than the nominal threshold of hearing. People debate whether or not this is due to effects of vibration on a house structure—this is for people inside a house—or whether it is a true perception of infrasound; but that does not really matter. The fact is that, at octave levels as low as 60 decibels, which is a very low level for infrasound, there can be adverse reactions from occupants. That data goes back almost 35 years.

Finally, I would like to—

CHAIR: Excuse me, Dr Swinbanks—

Dr Swinbanks : comment briefly on my own personal experience of wind turbine health effects. I was asked by some friends of mine to help them measure the infrasound levels in the basement of their home at the wind farm at Ubly in Michigan. It is noteworthy that this particular wind farm had been designed in 2005, at which time Dr Nina Pierpont, a doctor in New York state, had been opposing that wind developer because of concerns she had relating to the likely noise environment of a wind farm. She has been roundly criticised all around the world for supposedly promoting scare stories. But in fact the wind farm that was developed at Ubly by exactly the same developer has proven to demonstrate all of the adverse effects that Dr Nina Pierpont warned about. Indeed, 10 families ultimately took legal action against that wind farm. The matter was settled out of court. But the important point is that I myself experienced directly many of the effects that Dr Nina Pierpont warned about, and she certainly was not making it up. The fact is that these effects can occur.

In my particular case, I was working on a very calm evening when wind turbines were operating but there was very little wind at ground level and you could not hear the turbines at all inside the house. I actually had to keep going outside to check that they were still running. After three hours in the house I began to feel ill and I found that I was lethargic and losing concentration, but it was not until sometime afterwards that I began to realise that it was the wind turbines that were likely to be responsible. The level of infrasound that I was measuring was a level that I considered to be very low and definitely not a problem. After five hours in the house I was only too glad to leave, and I thought, 'At last I'm getting away from this,' only to find that, when I started driving, my driving ability was completely compromised. The front of the car seemed to sway around as I consistently oversteered. I had lost coordination and I had difficulty judging speed and distance. When I arrived home, my wife observed immediately that I was ill; she could see that straight off. And it took me a further five hours to finally recover and for the effects to wear off.

The important point about that incident was that I had considered that the conditions—a nice calm evening at ground level, but with the turbines still running—were extremely benign, and I had wondered whether I would even get any results. So I certainly was not anxious about infrasound. Similarly, when I got—

CHAIR: Excuse me, Dr Swinbanks—

Dr Swinbanks : Yes?

CHAIR: We have got very short time. Would you mind if we go to questions now?

Dr Swinbanks : Yes, that is fine. In fact, I had effectively completed, so that is fine.

CHAIR: We will start with Senator Urquhart.

Senator URQUHART: Thanks, Dr Swinbanks. I picked up, I think, from your opening statement that you live near an operating wind farm—is that right?

Dr Swinbanks : Yes. We have a farmhouse in Michigan, and the county, Huron County, in which we live decided that they were going to install very large numbers of wind turbines. They installed a first set at two locations in the interior of the region where we are, and the significant problems developed at one of those wind farms, but since then they have been installing progressively more wind turbines. We have an installation three miles south of us, which affects us only when the wind blows from a southerly direction and then only under certain weather conditions. But the intention is to install many times more turbines, and, essentially, the whole county will be covered in turbines if this situation continues as it is.

Senator URQUHART: Have you published any articles on infrasound from wind turbines in any peer-reviewed journals?

Dr Swinbanks : Not in peer-reviewed journals. I have presented, at conferences, the work that I have done, and it has represented a sequence of work. But I believed that it was better simply to get the information out into the public domain.

Senator URQUHART: In your submission you mention Steven Cooper's study from the Cape Bridgewater wind farm. Do you believe this was a scientifically valid study equipped to make conclusions about the link between participant sensations and infrasound?

Dr Swinbanks : I believe that in a situation where people are reporting the effects that they observe while at the same time the operating characteristics of the wind farm are being monitored remotely, if you find that there is then a close correlation between those two situations, when they are well separated and there is no communication between the relevant parties, that does imply that there is a significant link and that people are reacting to real events.

Senator URQUHART: We heard from the Association of Australian Acoustical Consultants. They had done a small statistical analysis of Mr Cooper's work. In this they found that Mr Cooper did not meet his hypothesis 63 per cent of the time. Do you think it is reasonable to suggest causality when a hypothesis is not meeting close to two-thirds of the event occurrences?

Dr Swinbanks : I would point out that I am not a statistician. I do not approach my own work from a statistical point of view. What I prefer to do is go and find out for myself what it is all about, and from my own experience I believe that what Steven Cooper has observed is entirely credible.

Senator URQUHART: Here in Australia we have had a population level study done that found no difference in the prescriptions that Australians had been given regardless of the distance that they lived from wind farms. Are you aware of any population level studies internationally that have found otherwise?

Dr Swinbanks : I am not aware of such studies. But I do know a lot of families whose life has been made pretty miserable by the wind turbines, and I find that every bit as impressive as the statistics that people collect. It is a characteristic of the medical profession that they operate hands-off and perform their evaluations entirely on a statistical basis. In the engineering profession, whenever possible we go and find out what it is like and subject ourselves to those conditions to gain an appreciation for ourselves. Sometimes I read documents from people who clearly have no direct experience. It is apparent from what they say. In this particular instance, occurrences are so comparatively rare amongst the general population that it is very easy to end up with a large number of negative responses and only a very small number of positive responses; yet the fact is that those positive responses can be directly associated with real problems.

Senator URQUHART: We are going to hear in a minute from Dr Leventhall. He has put forward in his submission that a much higher correlation in Mr Cooper's work could be found between audible noise and sensations rather than infrasound and sensations. Do you agree with Dr Leventhall that the correlation that Mr Cooper found is statistically much higher with audible noise than infrasound?

Dr Swinbanks : There are both components of sound present. The definition of infrasound, according to Dr Leventhall himself, is that there is a very fuzzy boundary between infrasound and low-frequency noise. He has stated that that often causes confusion. In reports that he has written his definition of infrasound versus low-frequency sound, which is generally considered to be audible sound: he has defined boundaries of 20 hertz on some occasions as being the boundary between the two effects—16 hertz. In a different report he talked of 10 hertz to 200 hertz. Finally he even proposed five hertz to 200 hertz in a 2006 paper. So the point is that this definition of where you are between infrasound and audible noise is a very flexible definition. I do not consider that it is particularly important whether the noise is truly audible or just perceived as a sensation. The important effect is that people do detect something; they detect a sensation and can tell that something is happening. I learnt this 30 years ago when I was working on a gas turbine installation. Initially, I was very insensitive to the sound but, ultimately, I could drive up in my car and detect that the gas turbines were running even before the car engine had been turned off. There was a very marked increase in sensitivity. So I do not really think that it is important whether it is audible noise or inaudible noise that gives rise to the sensation. The fact is: people do experience real sensation, and these sensations can be very unpleasant.

Senator BACK: You mentioned size of wind farms. Were you referring to numbers of turbines or the actual physical size of the individual turbines, or both, when you made your comments in that regard?

Dr Swinbanks : I am referring primarily to the number of turbines. That is obviously related to the overall dimensions of the wind farm. But I have in mind, in particular, the Macarthur wind farm, which has very closely spaced turbines. It has a very large number—something in excess of 140. People are, I understand, experiencing adverse effects at distances of three miles. I believe that is a consequence of a large, closely spaced wind farm. Whether the effects would be as severe if the spacing of the turbines is made greater, I believe that would relieve some of the effects. But I think the main issue is the sheer number of turbines.

Senator BACK: You mentioned about what the 2009 American Wind Energy Association report had failed to take account of. You made the reference to increased sensitivity over time—increased exposure—and you gave an example of your own situation with gas turbines. One of the witnesses who has appeared before us, Dr Tonin, from this Association of Australian Acoustical Consultants, put to the committee that you could undertake this testing for infrasound using a pneumatic signal attached to hearing protectors effectively in a quiet room for a limited period of time. I think he mentioned 15 or 20 minutes. Could you comment on how much value you regard such testing would be in trying to come to terms with our situation?

Dr Swinbanks : My attention was drawn to that paper, and I have read it. I have two immediate comments. Firstly, he was attempting to distinguish whether symptoms were due to actual infrasound or due to nocebo effects. The important point is: there are two different outcomes which could distinguish between those effects, but, in fact, there are many more than two possible outcomes from the experiment. There are up to 16 outcomes of which only two are definitive outcomes relating to nocebo effects or infrasound effects. When I looked at the data, the most impressive correlation that I could see from the data was that the sheer action of putting on the headphones appeared to have increased the symptoms of the people being studied by at least 44 per cent. This was an experiment in which putting on the headphones had a measurable effect. I would argue that we do not yet know what exactly the mechanism causing people to suffer adverse effects. As I indicated, NASA, 30-odd years ago, had shown that people could experience adverse reactions at what are nominally very low levels of infrasound, but that was in houses where there was possibly vibration from the structures—and we do not know whether people are sensing anything through their body rather than their ears, because people often report in low-frequency noise or infrasound environments that they can feel—

Senator BACK: Can I stop you there. We need to get the answers fairly quickly so that all of us can have a go. You made reference to the circumstances of your own experience, where the wind was gusting and then was not gusting and the sound of the turbines with each. Some people have put to us the idea that an average sound or an average level is adequate. You in your paper have suggested that the use of an averaging technique may be missing cumulative pressure fluctuations and, in particular, peak pressure. Could you briefly explain that further and whether or not there is a value in averaged sound or averaged levels of infrasound decibels, please.

Dr Swinbanks : My immediate comment is that there is no value at all in an averaged level. In that example I gave, if you average it all, you find that the wind turbine level if anything would be less than the gusting level and you would then conclude that the wind turbines are not significant, whereas in fact it is very clear that they are significant. But the other important point is that there is a very well acknowledged paper that was written in 2004 by two authors, Moller and Paterson, where they made it very clear that for the very low frequencies it is the actual shape and time history and peaks of the waveform that are important. In fact, Dr Leventhall, in an expert witness statement a couple of years ago, criticised me for supposedly not having read that report properly, but what I was doing was studying directly what the report recommended—namely, the time history and shape of the waveforms rather than long-term averaged versions of the waveforms.

Senator BACK: Thank you.

Senator LEYONHJELM: Dr Swinbanks, I have several questions. I hope we have time for them. Dr Leventhall was giving evidence in 2013 to a Vermont Senate hearing on the adverse health impacts of wind turbine operations in which he said they were 'made-up, make-believe', 'hoo-hah' and 'a propaganda technique'. I understand he also dismissed some of your work on impulsive infrasound. Has he communicated those concerns to you?

Dr Swinbanks : He has not communicated the concerns directly. I have known Dr Leventhall for 40 years, but until very recently I had not seen him for 20 years. I was quite surprised, when I met him, that he appeared to have a very different perspective on the noise conditions in America from the perspective he gave at that Vermont meeting. When he was in the UK, he told me that he thought the sound levels in America were disgraceful. At the Vermont conversation, he attributed problems to 'hysterical reaction'. The point is that permitted noise levels in the United States are significantly higher than in other countries and certainly higher than in Australia, so it is hardly surprising that there is what he called 'hysterical reaction'. You would certainly expect that, if people are subjected to more adverse conditions, they are going to react and respond more strongly.

But it most certainly is not hoo-ha. I can say that from my own experience. There is no question that there are some significant effects. We do not know precisely what the mechanisms are. But people did not know what the mechanisms for seasickness were for many hundreds of years, and they still recognised the existence of seasickness.

Senator LEYONHJELM: In the NASA work in the 1980s, Kelley describes in detail the physical sensations resulting from infrasound. Are his descriptions consistent with what residents are now describing as the physical impacts of wind turbine sound?

Dr Swinbanks : Yes, I believe they are consistent. These symptoms have been known for a long time. Dr Leventhall says they are entirely consistent with his knowledge of low-frequency noise. He does not find it surprising, but he argues that it is not due to infrasound. As I have indicated, Dr Leventhall has even defined low-frequency noise as being from five hertz up to 200 hertz, which overlaps very substantially a region that most people tend to call infrasound. So we have a situation where, for frequencies around 12, 13 and 14 hertz, do you say, 'That's infrasound. That can't be a problem,' or do you say, 'That's low-frequency sound. The symptoms are perfectly understandable'? The fact is it is a very fuzzy distinction and you can place yourself either side of that boundary dependent on precisely how you choose to define the boundary. I believe that the symptoms are consistent. They are certainly consistent with low-frequency noise. It is a moot point whether or not people are subconsciously hearing something. They are aware of something. I have no doubts about the nature of the symptoms.

Senator LEYONHJELM: I just want to ask you a few technical questions. Your submission had some graphs that showed the pressure fluctuations and frequency. Mr Cooper's report points out the need for narrowband measurements and not one-third octave bands for DBA or DBG when looking at infrasound and low frequency. Do you agree with that?

Dr Swinbanks : Certainly. I would not even dream of using one-third octaves or even averaging, over extended periods of time, just the pure spectrum levels. A proper analysis is both a narrowband frequency analysis coupled with a temporal analysis to look at the time history, as I commented earlier. If you go out to sea in a small boat, you do not worry about the spectrum of the waves; you worry about the shape of the next wave. This is what happens as you go down in lower and lower frequencies. For frequencies like 20 hertz and upwards, you tend to be more concerned with the blurring overall effect, but, as you get down to the very lowest frequencies, it is the shape of the individual waveforms that influences you. So one certainly should not be using these long-term averaging techniques.

Senator LEYONHJELM: Following up on from a question from Senator Back earlier in relation to peaks and averages, could you comment on whether or not it is possible to take a recording of infrasound or low-frequency sound—whatever you like—from a wind turbine and replicate it in a laboratory under controlled conditions in order to measure whether or not there is an adverse effect to it?

Dr Swinbanks : Yes, it is possible to do so, but the way in which people have been doing it so far, to me, seems a bit back to front. What they should be doing is, first of all, testing people who are known to be sensitive to wind turbines to try to find out what conditions enable an accurate replication of the effects. I do not see the point in just setting up an experiment in a laboratory and saying, 'We didn't observe anything' if you have not first established, for a person who does suffer ill-effects, whether or not they actually respond to that test. There are real questions about what exactly are the important effects and what exactly should be reproduced in a laboratory. For example, I have quoted the NASA work of 30 years ago. People consider that, possibly, it was the vibration of the structures that people were sensing rather than the physical pressure variations of the infrasound. We do not know exactly what gives rise to the adverse effects. One has to validate any laboratory testing by being satisfied that people who are sensitive and have reported adverse effects can indeed experience those effects under the test conditions.

Senator CAMERON: Thank you for being here, Dr Swinbanks. You are three miles from the wind farm—is that correct?

Dr Swinbanks : That is correct.

Senator CAMERON: Was your house there before the wind farm was built?

Dr Swinbanks : Yes. I must make it clear that I am not directly complaining about those noise levels because at the moment the effects occur only when the wind is blowing from the south, which is only five per cent of the time. They only occur under circumstances of very severe temperature inversion. So it is a very occasional event. The point is simply that it can occur, and people who are in a position where they are encountering those sorts of conditions more frequently could also be expected to encounter such effects at such distances. The point that I am making is that such effects can be detected at these distances, not that those effects are a significant intrusion at the moment. But I would point out that in the future they are proposing to build turbines not just to the south of us, but to the west and the north-west, in which case those conditions may prevail for 35 or 40 per cent of the time. The fact is that modest numbers of turbines at sensible distances are not generally a consistent problem. Large wind farms operating under adverse circumstances can indeed be a significant problem at those sorts of distances.

Senator CAMERON: So when the turbines started to be built, was there an opposition group formed in your area?

Dr Swinbanks : There was never an opposition group as such, but there were a significant number of people who were making known their concerns. There was not a formal opposition group, but people were making known their concerns. The fact that there were two wind farms built at an early stage meant that people had some experience of what could be happening. The interesting feature was that you might say that those two wind farms, if you looked at them initially, looked pretty similar and pretty comparable; but one of them gave rise to very severe problems, while the other one did not appear to give rise to anything like as many complaints. The skill of constructing a good quiet wind farm is still pretty well lacking. It is very much a trial and error process, unless people obey sensible guidelines like ensuring that the separation between the turbines is of a sensible size and they are not choosing to mount turbines in locations, for example, on ridges where there can be a significantly distorted wind pattern and shear flow effects. The point is that there is a difference between a well constructed wind farm with sensible spacings and numbers and a poorly constructed wind farm.

Senator CAMERON: You also indicated that an inversion caused problems, and you gave evidence in relation to one night when it was not windy, and you had to keep going outside to check if the turbines were operating, then you became lethargic, you were losing concentration, you lost coordination when you were driving. Were you the only one in your household who had these symptoms?

Dr Swinbanks : It was not my household, it was the house belonging to some people who lived at the wind farm, who had asked me to take the measurements for them. Those people have experienced adverse effects to the extent that they actually had to rent alternative accommodation and go and sleep in the alternative accommodation at night. They initially tried to look at weather forecasts and decide if they could sleep in their own house or not, but they ultimately decided that the wind conditions could change during the night, and it could go from a benign night to a bad night. Therefore they began to sleep away from the property routinely and regularly. The particular point that I should like to make is that I was extremely surprised to experience these symptoms. I thought it was a non-event. But one particular point was that I was using a computer very extensively, and if there is a relation to motion sickness, I would certainly comment that if I am in a motor car and I try to use the computer or read—assuming I am not driving—I can very quickly become ill. I wondered whether this was purely conjecture, whether the fact that I was concentrating on using a computer actually enhanced the severity of the effects.

Senator CAMERON: Are you aware of the study that was done by Fiona Crichton, George Dodd, Gian Schmid, Greg Gamble, and Keith J. Petrie, titled 'Can expectations produce symptoms from infrasound associated with wind turbines?' It was a peer reviewed analysis reported in Health Psychology. They indicated that if there were high expectancy that you would get sick from infrasound then you would become sick. They did work with infrasound and sham infrasound, and it really did support the analysis that the psychogenesis and nocebo effect were real. Have you had a look at that?

Dr Swinbanks : Yes, I am familiar with that and I wrote a criticism of that document at the time. The point was that the difference between their sham infrasound and their real infrasound was essentially negligible. The real infrasound was at a level of 40 decibels, which is very low, and not surprisingly there was no difference in the response of any of the people between the sham and the actual infrasound. The other point is that the duration was only 10 minutes. In the effects that I described it took five hours for the full effects to become apparent.

I have related that whole situation to sea sickness. It used to be the case, in the 1970s, when I did a lot of sailing, that one would frequently encounter people who considered that seasickness was just psychological. Very often, they learned the hard way that it is not. But the point is that, if you wanted to test two groups of people for seasickness, you would not put two separate groups into two separate boats and put them on a flat, calm lake for 10 minutes and then announce that any reactions prove that seasickness was caused by a nocebo effect. That would actually be regarded as a joke. So I am afraid that I consider that that particular experiment was more an experiment in a pretty obvious psychology than anything relating to the validity of whether infrasound represents a real problem or not.

Senator CAMERON: So many questions, so little time. Thank you.

CHAIR: Dr Swinbanks, is the sound pressure level important when considering biological effects of infrasound and low frequencies, or could it be the frequency via acoustic resonance?

Dr Swinbanks : I think I should make it clear that I am not a biology specialist, so anything I say is amateur in that context. But I believe that the long exposure times can be a factor in inducing effects in people. Again, drawing a parallel with seasickness, it was not uncommon to go to sea for eight, 12 or even 24 hours and think, well, you are not going to get seasick this time, only to discover suddenly at the end that you do in fact start to succumb. In that context you can find that the onset of the symptoms can seem to be very rapid, even although you have been exposed for a long duration. So I think there are important considerations relating to duration of exposure.

I point out briefly that Dr Alec Salt, who is an expert on the characteristics of the cochlea, has suggested there is a phenomenon known as temporary endolymphatic hydrops, which is a progressive swelling and blockage of the little pressure relief hole at the end of the cochlea. If that becomes blocked then you can become very much more sensitive to infrasound. So it is quite possible to hypothesise that long-duration exposure is causing a blockage to progressively develop, and when it becomes severe then the person will start to experience much more extreme effects from the sound pressure than they would if there were no blockage.

So you could imagine in those circumstances that there might be a protracted period where there was no effect and then a comparatively rapid onset of effects. It would then take time after the exposure for those effects to clear, so you would then have persistence for some time afterwards. This is a whole area that requires a great deal more study. One of the conclusions, though, of the original 2009 AWEA report was that there was no need for any further research. I would completely disagree with that. I think it is apparent that people are now taking the issue seriously and at last people are beginning to investigate more thoroughly exactly what may be happening.

CHAIR: From what you have told me, I take it that the level of sound pressure is less important?

Dr Swinbanks : There are several factors that are important and when they come together they can effectively reinforce one another. I am not certain that you can take out one specific component and reject the rest. It is a combination of different contributions that can ultimately lead to the end condition. But the obvious conditions are length of exposure, sound pressure levels but also the frequency and the nature and character of the time history of the wave forms.

CHAIR: Thank you. We are running over time. If there are no further questions—

Senator BACK: I have one, but it will have to go on notice.

CHAIR: Dr Swinbanks, there may be further questions placed on notice by senators. We would appreciate it if you accept those and respond.

Dr Swinbanks : Certainly.

CHAIR: Thank you for your appearance before the committee.

Dr Swinbanks : Thank you for giving me the opportunity to speak. I am very grateful for that.

CHAIR: Thank you.