Microseismic and Infrasound Monitoring of Low Frequency Noise and Vibration from Windfarms

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Excerpt from the Keele University Applied & Environmental Geophysics Research website:
Because of our previous, unique experience in monitoring seismic vibrations from wind turbines in the UK, the Applied and Environmental Geophysics Group of the School of Physical and Geographical Sciences, were asked by the MOD, the DTI and the British Wind Energy Association to investigate whether there was a solution to this impasse. By carrying out a detailed programme of seismic and infrasound measurements in the vicinity of several wind farms in Scotland we were able to identify the characteristic frequencies and mode of propagation of seismic vibrations from wind turbines and develop a model for the integrated seismic vibration at the Eskdalemuir site which will be created by any distribution of wind farms. By setting a noise budget which is permissible at Eskdalemuir without compromising its detection capabilities, we have demonstrated that at least 1.6 GW of planned capacity can be installed and have developed software tools which allow the MOD and planners to assess what further capacity can be developed.

The MOD have now lifted the 80 km exclusion and any further wind farm proposals will be assessed against criteria established by this study.

4 thoughts on “Microseismic and Infrasound Monitoring of Low Frequency Noise and Vibration from Windfarms

  1. WELL! I read until I was crosseyed and I still don’t know how far low frequency vibration can travel! With eight wind turbines next door to me, I presume the closest at 550 meters, will my home and body vibrate or not??? A simple yes or no will do!

  2. The study in Scotland was to determine the potential interference that seismic vibrations produced by distant IWT(s) could have upon the sensitivity of a seismic detection facility which was designed to detect the faint seismic vibrations generated by the launch of intercontinental ballistic rockets part way around the world.

    The concern was that IWT’s could render the seismic detection facility ineffectual and thereby compromise British national security.

    The intent of the study was not to measure aerial infrasound. The issue of seismic waves being generated by IWT’s hasn’t played a part in any studies to date on the health effects of IWT’s. Rather, WTS is the result of aerial infrasound impacting directly upon live bodies.

  3. Refer to page 53 of the study. The map is marked in UTM (datum, projection not stated) so from 349 to 350 is 1KM (1000 meters) etc. That gives you an idea of the distance of the sensors. Some of them are several kilometers distant.

    The Monitoring stations were from approximately 2 to 6KM away — more or less from the Dun Law Wind Farm.

    I think the graphs on pages 59 through 65 are in DB.

    If so, they clearly show that Vestas (for example) would need a much greater set-back than 1KM — since the noise exceeds 60dB and is up to 70 dB in some cases (12m/sec wind velocity). AT 7.29 m/sec it is still reaching 60 dB (assuming that is the left scale).

    If the graph is not in dB maybe someone could clarify. I only had a few minutes to read the study.

    I think this makes the case that that at 500M the turbines would exceed the allowed 50-55 dB standard.

    At the very least it proves that a study for the purpose of human discomfort/distress and irritation is required.

    This study as Barry points out was not intended to make these points, but I believe that it points the way to the need for a proper health effects study.

    By itself, the study shows enough to concern me that if it were in my power I would shut down any turbine withing 2KM of a dwelling. This would be based on the 60-70 dB noise level at 7.29 to about 12m/sec wind velocity. (assuming that it is dB)

    The study does not investigate the “beat note” effect. Nor does it concern itself with flicker effect — which are two additional issues.

    Hope that helps.

  4. Part of the study was concerned with determining if airborne infrasound waves could be producing the surface seismic waves that were being detected by their seismic sensors. In order to address that issue, they acquired infrasound detecting microbarometers, interestingly some of which came from Dr David McDonald of the Canadian Geological Survey (page 53).

    They wanted to determine if there was a direct frequency coupling between the wind turbines’ “blade passing and structural resonance of the towers” and the infrasound being generated by the wind turbines’ operation (page 53).

    They did determine that wind turbines cause infrasound which can be detected at many kilometers (pages 76 and 77).

    However, they concluded that the seismic vibrations they were concerned with travelled directly through the ground as “Rayleigh waves” (page 67).

    The majority of their infrasound testing was conducted at a distance of approximately 6 kilometers (map, page 55).

    A closer infrasound measuring station was located at Kelphope, 2 kilometers from the windfarm. At this distance during substantial windspeeds and turbine activity, the turbines’ infrasound harmonics were clearly detected. However, over the intervening 4 kilometers to the other measuring stations, those characteristic infrasound harmonics were reduced and eliminated by the substantial wind turbulence over that landscape (page 67).

    Obviously, this study does indicate that the distance between the Ontario 550 meter minimum setback and the 2+ km distance (represented by the Kelphope sensors) is the realm that exhaustive studies should be done .. employing infrasound detecting barometric equipment in the same league as that used by those conducting this seismic study.

    The above page references can be either accessed directly from the report or can be viewed at .. http://www.algonquinadventures.com/waywardwind/images/Infrasound-Seismic-Info.jpg

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