What wind swindlers always knew about turbine noise – the technical stuff

It’s hard to keep them buried forever.

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In our last post we covered the Graham Lloyd piece in The Australian on what the wind weasels have always known about infrasound and low frequency noise from giant fans and the impacts on neighbouring victims.

We don’t like to gloat – but it was one of our research team that dug up the papers from NASA’s archives that featured in the Oz article.  For the benefit of the technophiles, our engineering team has put this summary together on the research that looked at the impacts on families from a single turbine which – by comparison with the latest 3MW monsters – was just a pup.

In 1987 I was top dog – 30 years later – I’m just a pup.

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Knowing the way wind scammers and their pet acoustic goons treat anything that runs counter to their piffle about turbines being quieter than Kelvinators at half-a-click – it comes as no surprise that they’ve kept a lid on this systematic, collaborative research done in the 1980s.

The work looked at the suffering caused to neighbours by a single fan in North Carolina.  The level of sophistication and scope of the study – headed up by a brain-box called Kelley – hasn’t been matched until the very recent work by the team at Shirley Wisconsin and now being replicated at Waterloo SA by Professor Colin Hansen, Professor Con Doolan and Steven Cooper.

In the period between now and then – there has been NO research done or funded by the wind industry that has bothered to take noise testing kit inside homes where the problem is (with the exception of the whitewash dished up late last year by SA’s EPA in collaboration with wind industry favourite – Resonate – that deliberately excluded frequencies above 20hz and made unsubstantiated claims about hearing thresholds. “Infrasound” is – by definition – “inaudible” – but is felt and therefore perceived).

NONE of the wind farm noise guidelines that apply in Australia require acoustic testing for low frequency noise – and none require any testing at all INSIDE homes – but why would they? They were written by the industry – the SA EPA guidelines (which NSW copied for theirs) were written by Sonus which runs with the wind wolf-pack.

STT is never overly suspicious but our “Spidey-senses” have been tingling since we dug into the work of Kelley & Co.

Could it be that the wind weasels and their goons knew about the approach taken by Kelley & Co all along and tailored their wind farm noise guidelines to avoid the bleeding obvious?

If you don’t want inconvenient answers – don’t ask inconvenient questions.  If you already know what it is that’s driving people mad as they try to sleep in their beds (strangely enough located INSIDE their homes) isn’t it just plain commercial sense to stick your monitors outside in a paddock under giant gum trees and take a few hours of noise data during the day time (as the SA EPA does with its kit)? That way you’ll never find out what’s going on inside at night-time when heads normally hit their pillows – and you’ll never have to answer for it. Business as usual.

Back to the study. The fan in question was designed by NASA and could generate 2MW – when the wind was “just right” – it had 2 blades – each 30m in length – and sat on a 40m tower (see the pic below). That compares with the latest Vestas behemoth – the V112 – which has 56m blades on a 100m tower and punches out 3.5MW when wind conditions are right.

The research, which started in the late 70s, was based around this turbine sited near the town of Boone in North Carolina (Kelley et. al., 1985; p. 1)

MOD-1 Turbine in Boone, North Carolina. Installed in 1979.

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They found that a sub-population of the community (12 families from approximately 1000 households within 3 km) suffered on some days, while others didn’t report any problems. The affected people reported rattling of objects, falling dust, an intermittent thumping, vibrations, sensations that they could feel rather than hear, creating a sense of uneasiness and personal disturbance. They reported the “sounds” were often louder inside their homes and that some rooms were worse than others (Kelley et. al., 1985; p. 4-5).

If you think the sensations and symptoms being recorded by Kelley & Co are a thing of the past – then compare the scientifically documented experiences of the victims of NASA’s fan with these from current victims:

• a family living with turbines at Cape Bridgewater
• a family near turbines at Waubra
• another person from Waubra
• and this person living next to turbines at Lake George

Our lexicographers couldn’t find a reference to Nocebo prior to 2012 – when some quacks in the employ of the wind industry made it up and greentards started running with it. So we’re pretty confident that the North Carolinians weren’t victims of a theory that was yet to be invented. Invented that is – as a smoke screen for the harm being suffered from Canada to Denmark, Scotland to the Netherlands, Taiwan to Australia.

When precisely the same complaints cropped up in 1979, a group of REAL scientists and researchers from multiple prestigious organisations – such as MIT, NASA, University of Virginia and Pennsylvania State University, joined the then Solar Energy Research Centre and the General Electric Company to have a good hard look at what was going on (Kelley et. al., 1985; p. 5-6).

Unlike the current crop of pseudo-scientists that back the wind weasels to the “last man and the last shilling” – these bright boys and girls actually went to where the problem was and – heaven forbid – went INSIDE the homes of the affected people and – HORROR – SPOKE to them – on 5 field trips over 2 years.  As real scientists – keen to find answers no matter what they might be – they went in hard to unravel the problem and did it in an exhaustive and systematic way – (Kelley et. al., 1985; p. 8-11). No DENIAL and no EXCUSES to be seen here.

For example, they did a series of seismic studies (Kelley et. al., 1985; p. 10) that showed that what ever was responsible for the annoyance was coming through the air, rather than through the ground (Kelley et. al., 1985; p. 30-34).

The acoustic experts on the team pulled out all stops to understand, measure and map what was happening.  There were at least three different sources of noise produced by the MOD-1 turbine. However, the bulk of the sound pressure was found to be occurring in the low frequency range (Kelley et. al., 1985; p. 12-13).

Comparing the frequency of noise – lower frequencies have spread out waves, higher frequency are closer together. The unit is Hertz (Hz) – the number of cycles per second of a periodic phenomenon

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They compared their data from the people impacted by the MOD-1 turbine with that obtained from a known low frequency noise source. These were residents of Oregon who had been annoyed by another type of machine, gas-fired peaking generators – these victims also reported little audible noise, but had feelings of pressure, uneasiness and vibrations (Kelley et. al., 1985; p. 182-187).

The meteorologists on the team mapped the conditions in the atmosphere to correlate wind and weather with periods when “annoyance” was present  –  (Kelley et. al., 1985; section 6.0 p. 157-171). Sound ray paths were mapped to examine how terrain impacted on the sound propagation (Kelley et. al., 1985; p. 160-168).

The sound rays produced by the wind turbine on the hill on the left, travel to the right and reflect off of the terrain and impact on houses 7 and 8 (in the centre of the image). Figure 6.7 in Kelley et al., 1985.

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Note that “annoyance” is a term used in acoustics for noise related sensations and symptoms – including sleep disturbance and is not simply noting a person’s “dislike” of the noise source.

The researchers concluded that the main culprit driving the locals nuts was low and very low frequency noise (<20Hz) (Kelley et. al., 1985; p. 20; p. 34). The researchers did not, however, use the term ‘infrasound’, but called everything low, or very low frequency noise – and the fan in question produced buckets of it – especially notable as the blade passed the tower.

The researchers found that the turbine-generated sound energy interacted with the structures of homes – amplifying low frequency noise from the turbine (much like banging on a drum – with the house being the drum) and this structural resonance increased the level of annoyance suffered by those inside (Kelley et. al., 1985; p. 21; p. 34). The noise levels measured outside homes were lower than the levels measured inside (Kelley et. al., 1985; p. 26 -31). For those residents that were severely impacted, the researchers found turbine-generated internal acoustic pressure was particularly acute in some rooms – often when the room’s wall was facing the source of the low frequency noise – ie the turbine (Kelley et. al., 1985; p. 187).

Turbine blade rotation speed and wind direction also impacted on the amount of sound energy detected and the annoyance experienced (Kelley et. al., 1985; p. 77). The meteorologists on the team worked out that certain weather conditions could have very strong impacts on noise levels – which in turn would combine to react with certain types of terrain (Kelley et. al., 1985; p. 33-34; 168-171).  In certain weather conditions “adverse noise propagation” could occur in such a way that it did not matter if the home was upwind or downwind of the turbine; and the combined effects of weather, atmospherics  and terrain could result in noise levels 25dB or more greater than researchers expected for a given distance (Kelley et. al., 1985; p. 168-171).

Back in 1985 – the researchers concluded their book (Kelley et. al., 1985; p. 226-227) with answers to questions that current victims know too well – and which the wind industry and their pet acoustic consultants have been denying or spinning away – since giant fans started popping up like mushrooms a decade ago:

Why did the noise not reach annoying levels each time the turbine was operating?

We have shown that the characteristics of the tower leg wakes were very important in whether or not strong impulses were produced. These characteristics (vortex strength, in particular) are functions of the freestream velocity, turbulent energy levels in the critical Strouhal shedding frequency range, vertical shear and stability, and upwind fetch. Further, certain wind directions tended to orient the turbine and its radiating lobes away from the most frequently affected homes at times, or a combination of terrain and atmospheric refraction failed to focus the sound sufficiently to be heard.

Why were some families annoyed more often than others and why did the situation confine itself to such a small fraction of the overall population living within 3 km of the machine?

Again, the reason why certain homes were affected more frequently was because of three factors: (a) the orientation of the turbine (which positions the lobes of the acoustic dipole in their general direction) (a function of the site climatology); (b) the terrain along the centerline of these dipoles; and (c) the vertical variation of wind speed and temperature. By far, factors (a) and (b) appear to be the most influential, since they both subsequently have an influence over (c). Figures 6-5 through 6-9 show sound ray paths for various radial directions from the turbine, and the importance of the terrain is clear. The small population fraction bothered by the turbine happened to live in locations where a combination of terrain and refractive focusing reached maximums, or caustics, a good portion of the time.

Why did the noise appear more noticeable inside the affected homes and why did it become more persistent and perhaps louder during the evening hours?

The noise was more noticeable within the homes because of the dynamic amplification and resonances created in the internal acoustic pressure field because of the interaction between the external transient acoustic loading and the lightly damped elastic response of the residential structure. This dynamic interaction serves to extend the impulse time period from a few milliseconds outside to more than a second indoors. There were two reasons why the sounds became more persistent and perhaps more severe at night. The first reason again relates to the site’s climatology, in which the diurnal variation in wind speed tends to reach a maximum during the period slightly before local sunset and continues up to the early hours of the next morning, with a secondary peak occurring just after local sunrise and continuing for one or two hours thereafter. A coupling of this evening wind-speed maximum with the second reason, the transition from a daytime to nocturnal atmospheric surface layer, in which the surface to hub-height stability increases and encourages the development of turbulent shear layers, resulted in a greater degree of Strouhal excitation of the tower leg wakes. This combination of higher wind speeds and Strouhal excitation increased the intensity and 2-D structure of the embedded wake vortices and, subsequently, the severity of the impulse generated by the turbine rotor blades. These conditions may have persisted for up to four or five hours, depending on conditions, and therefore appeared more severe and persistent to the affected residents during those periods of the day. Furthermore, generally lower ambient noise levels occur during the early evening hours, which perhaps also contributed to the increased sensitivity of the affected residents (Kelley et. al., 1985; p. 226-227).

The researchers likened their field studies to a fishing expedition – they would hope that they were set-up at the right place, with the right equipment, at the right time. Sometimes they got very little, but there were enough successful field trips to show – without doubt – that turbine-generated low frequency noise was a major problem inside homes – at distances out to 3km.

The difference between the wind weasels’ acoustic puppies and these researchers, is that Kelley & Co set out with open minds and were keen to find the source of an actual problem – instead of trying to liken the noise to fridges (anyone heard of people abandoning homes due to a noisy Kelvinator?) or claiming that turbine noise is like the gentle lapping of waves on a moonlit beach.

Some of the research team’s members persisted in their efforts to better understand how low frequency noise was impacting on people. So they took their data and insights from their work on the MOD-1 turbine and created a controlled environment in an effort to replicate the acoustic environment observed in the actual homes they first studied.  The aim was to improve the understanding of what types of noise caused the most problems for people, and how to go about measuring that noise in the most meaningful way (Kelley, 1987). In particular, they wanted a better understanding as to why wind turbine low-frequency noise was found to be so much more annoying inside people’s homes – and what would be the best way to measure it?

So they built an experimental house. They generated noise profiles similar to those of the MOD-1 wind turbine at one end of their model house and measured that noise at the other end. They put their listeners (n=7) in the middle room and asked them to note how they felt while they subjected them to three different patterns of sound meant to represent either a single turbine, an array or turbines, turbines working at various speeds, a number of turbines that were pulsing periodically (“periodicity”) and others that weren’t showing periodicity. They also included some masking noise at various points in the listeners’ exposure to the noise (Kelley, 1987; p. 3-4).

The experimental house (Kelley, 1987; p. 3)

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The noise produced was analysed by various metrics such as the standard A and C weightings, and the weightings they believed were more suited for measuring low frequency noise – the G1 and G2 weightings and the Low Frequency Sound Level (LSL) and Low Frequency Sound Pressure Level (LSPL) weightings.

The participants were asked to listen to an assortment of these noises for 45 minutes and record their sensations, noting the time of their experiences. The annoyance categories the participants were asked to respond to were:

• loudness or noise level
• overall degree of annoyance and displeasure
• sensations of vibration or pressure
• the sensing of any pulsations

Their results (Kelley, 1987; p. 6) confirmed that

1. People do indeed react to a low frequency noise environment;
2. A-weighted measurements were not an adequate indicator of annoyance when low frequencies were dominant; and
3. The highest ranked predictors of annoyance were the LSL and C weightings.

Given that all of this has been settled science for almost 30 years – STT puts the following posers:

1. Why are all wind farm noise guidelines concerned – and ONLY concerned – with dB(A) – the A-weighting?
2. Why do those same guidelines EXCLUDE the need to measure low frequency noise INSIDE homes?
3. Why do those guidelines set measurement criteria that – instead of measuring noise inside homes – permit noise measurements to be carried out with testing kit set up under giant trees or stuck in bushes?

No prizes for the obvious answer to all of the above: the wind industry had its goons write the noise guidelines.

If you need a licence to ride rough-shod over hard working country people – then you sure as hell don’t want anyone to look at the source of the problem – which your team has known about for over a generation.

So the lessons the wind weasels picked up from all this can be summarised as follows:

• set the noise guidelines to cover up the obvious;
• pay a crack team of spin doctors and hack pseudo-scientists to run “interference” for you;
• be prepared to lie to Senate Inquiries
• whinge, dodge and avoid the imposition of reasonable noise standards – that apply to all other industrial noise sources; and
• when the victims start to become vocal and obvious PR problems – buy their homes using money from the REC tax on power consumers and then bulldoze them.

Some call it wind swindling – I call it a way of life.

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The papers referred to are:

Kelley, N. D., McKenna, H. E., Hemphill, R. R., Etter, C. L., Garrelts, R. L., & Linn, N. C. (1985). Acoustic noise associated with the MOD-1 wind turbine: its source, impact, and control. US Department of Energy.  Book -PDF download

Kelley, N. D. (1987). A proposed metric for assessing the potential of community annoyance from wind turbine low-frequency noise emissions. Presented at Windpower’87, San Franscisco, Calif., 5 Oct. 1987 (Vol. 1). PDF Download