In a radio interview on 11/3/2010 with Dale Goldhawk on Zoomer Radio AM 740 Toronto, I made the statement that “the 550 meter setback distance between wind turbines and people's homes was absolutely insane”. I stand by that statement.
It is often said that the definition of insanity is to do the same thing over and over and expect a different outcome. Engineers have known for years that low frequency sound disturbs people intensely. In a presentation given on Sept 9 in Birmingham, UK, Malcolm Swinbanks, an engineer with years of experience in infrasound issues presented data from his own work with gas turbine sounds in the 1980's, as well as NASA research showing that low frequency sounds disturbed people. He estimated that modern wind turbines are likely to influence about 10% of young adults.
This was all known 20 years ago !!!
So putting up wind turbines, which are known to generate infrasound, near peoples houses and to expect to NOT cause problems in my view is the height of insanity. It is just generating more and more people with problems.
If you look at the relationship between annoyance and different noise sources you can see that wind turbine noise is clearly “different” from other types of noise . Comparing with aircraft, automobile or rail traffic wind turbine noise at about 30 dB lower levels (40 dBA rather than 68 dB A or higher) annoys 30 % of people. There are attempts to justify the increased annoyance by other (e.g. visual) factors but the possibility remains that the noise itself could be more annoying, due to the infrasound that is present in the noise but which is excluded from the A-weighted measurement.
The problem is also well demonstrated by the following chart put together by Stephen Ambrose and Robert Rand of Rand Acoustics (click link for more details). It shows how annoyance and complaints are related to the sound generated by turbines.
The first thing to note is that the Leq represents the A-weighted noise level (i.e. only the sound you can hear). In order to get very few complaints, the Leq of wind turbine noise must be 30-35 dBA or lower. This is a remarkably LOW level compared to other types of noise such as road traffic. This alone tells you that wind turbine noise is “different” from other types of noise. It is more annoying. And the reason people find it annoying is because of the high infrasound component which is not measured in this dBA reading, but is detected by the human ear. So, even though your refrigerator may make a higher sound level, your refrigerator isn't so annoying and doesn't keep you awake at night because your refrigerator is not generating infrasound to the same degree. If you keep following the readings up the curve, at 35 dB, 6% of people will be bothered/annoyed, at 40 dB about 25%, and then at 45 dB about 85% will be annoyed by the noise. (Note that the upper part of the curve is an interpolation based on Pederson et al.'s report of 45% of people annoyed at 42 dB A).
So, when the wind turbine companies negotiate allowable Leq levels of 45 dB or higher, and then put in their turbines which generate noise at that level, and then are surprised when people start complaining. That is totally insane. The complaints, the annoyance and the subsequent health problems from the chronic annoyance and sleep deprivation that result are ALL TOTALLY PREDICTABLE.
Why turbine companies want to keep putting these devices close to peoples houses is difficult to understand. One quick answer could be that $ matter more than people. But it is more complex than that. The real answer is that those whose jobs depend on the wind turbine companies, the consultants, the engineers, and the politicians who support wind energy for green reasons, they have all drunk the “Kool-Aid”. None of them want to hear that they may be a problem. Now, the situation has become so dire that no-one associated with the wind turbine companies dares raise their head and accept there is a problem. It has become like a religion or cult. It is the “If you are not for us, you are against us” mentality. Anyone who accepts there may be a problem will be immediately cast out. In my view, it is the engineers and experts who should have known better who are the real cause of this problem. They have let the wind turbine companies down by not preparing them for this possibility. To me, I see the data above and have no doubt there is a problem. For those in the wind turbine community, they see the data above and say it just can't be true. How can such a low sound level cause such a problem? Gosh darn it, my refrigerator is louder than that and I live with it.
The reason why wind turbine noise is more annoying than a refrigerator is because the wind turbine produces high levels of INFRASOUND !
If you don't understand the infrasound problem then these Leq annoyance curves do not make sense. The annoyance Leqs are low because they are only looking at part of the noise, the part you can hear. And the part you can hear is not the most annoying part.
So, the problem is that in most cases, setback distances are either not based on sound generation or they are based on A-weighted sound levels. In some cases they are based on safety aspects, so flying parts don't come through the roof of one of these machines falls over. These setbacks are typically much lower than those based on sound levels. The 550 meter setback is apparently intended to keep the sound level at people's homes below 40 dB A. As we can see from the above graph, that will leave 25% of the people living there annoyed for the rest of their lives living in their home, except on calm days or until they decide to move. So instead of claiming that these are really low sound levels that couldn't possibly affect anyone, the sound levels considered need to include G-weighted or comparable measures of the INFRASOUND, bearing in mind that infrasound at approximately 60 dB G stimulates the inner ear. The A-weighted (dB A) measurements on which decisions are presently based totally ignore the infrasound component and thus ignore the documented infrasound problem. Pretending the infrasound problem doesn't exist, won't make it go away. Instead, putting up more of these devices close to people's homes just gives us more subjects to study, more people to file lawsuits, and more people who quite predictably get annoyed. The wind turbine industry has to come to terms with this reality.
Last edited 12/28/2010