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Unexplained Low Frequency Noise

Note:  Technical papers distinguish infrasound (below 20 Hz) from low frequency noise (20-200 Hz), since 20 Hz is the lowest sound frequency considered by “experts” to be audible to humans.

I have used the term Low Frequency Noise (LFN) in this document to refer to all sound frequencies below 200 Hz since I do not know what spectrum of low sound frequencies my wife is capable of hearing.

Executive Summary

On behalf of my wife and other people who are sensitive to LFN, I am writing these notes based on recorded and anecdotal observations made over a 3-1/2 year period.

My wife and other people started hearing an unexplained intermittent low frequency noise (LFN) the autumn/ winter of 2006 – at about the same time a wind farm was commissioned nearly 25 miles SE of our home. Prior to this time they never heard any unexplained LFN.

Our hypothesis is that that the audible LFN is emitted by one or more wind farms. Even though we live a considerable distance (10+ miles) from the nearest wind farm – and are out of sight of any wind farms – the LFN can occasionally cause a minor adverse affect my wife’s health when it is particularly loud.

Even though we do not yet have sufficient data to conclusively prove our hypothesis, with wind farms encroaching ever closer to our quiet rural home, I am concerned about the adverse effects the LFN will have on my wife’s physical and emotional health in the not too distant future – if (or when) my hypothesis proves to be true.

As wind turbines continue to get larger and larger, the low frequency (LF) spectrum of noise emitted by wind turbines becomes lower and lower. The use of A-weighted noise measurements, under current ETSU-R-97 noise assessment guidelines for wind farm developments, disregards most of the LFN spectrum emitted by wind turbines. The current regulations make it extremely difficult (if not nearly impossible), for people severely affected by wind farm noise, to get adequate protection from noise regulations governing wind farms.

Another effect of LFN, not covered by noise measuring procedures in ETSU-R-97, is that of resonance – the walls of an enclosed space are capable of resonating low frequency sounds (much like the sound box of a musical instrument) – with the lowest resonant frequency being dependent on the dimensions of the room. This resonance appears to amplify LFN levels indoors. Again ETSU-R-97 procedures to not take this phenomenon into account.

Therefore, people sensitive to LFN have no legal protection from the adverse affects of LFN emitted by wind farms due to inadequacies of the ETSU-R-97 guidelines.

Because of the lack of legal protection offered to LFN hearers by ETSU-R-97 I have serious concerns for the health and well being of my wife, and others, in the not too distant future. I have therefore concluded that I have no option but to put my hypothesis into the public domain now in the hope that my hypothesis will be subject to independent scientific testing.

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