Wind Power Handbook

By Timlynn Babitsky
The claim by wind power resistors that “infrasound” is a health problem for people living anywhere near modern wind turbines is not supported by facts. There is general agreement among acousticians that infrasound from wind turbines is not a problem. There is a turbine noise issue to which we do need to pay attention, but inaudible noise making your body parts vibrate is just not it.

Infrasound is sound with a frequency too low to be heard by the human ear – in general it is bass waves with a frequency below 20 Hz to 22 kHz.

We are surrounded by and have evolved within an environment of naturally occurring infrasound — ocean waves, wind, earthquakes, pounding surf, waterfalls, hurricanes, thunderstorms, and anything that produces a naturally occurring slow oscillation of the air.

And of course, there is a whole lot of human generated infrasound – from slow speed fans to engines, cars, buses, trains, motorcycles, airplanes, explosions, and machinery.

Yet the fuzzy connection between wind turbine infrasound and risk to human health continues. It hinges on the idea that high levels of low frequency noise excite the body to vibrate, most notably in the chest, and that profoundly deaf humans perceive noise through vibrations in their bodies. But the thinking is circular to claim that wind turbines generate inaudible infrasound that “can be felt but not heard” and that this infrasound vibrates the chest with dire health risks.

To begin with, the noise frequency levels that produce body vibrations are well above the hearing threshold. You would hear the explosion, crash, or band speakers cranked to their maximum loudness as well as feel them, unless you were profoundly deaf. So the idea that unperceived wind turbine infrasound is pounding your body and making you sick – is another one of those “we don’t want wind turbines” myths.

On the other hand the “problem noise” that does come from wind turbines is the fluctuating swish sound of the blades passing the tower, which does irritate some people who are highly sensitive to fluctuating sound.

The problem is that wind project objectors use acoustic terms like infrasound incorrectly. They indicate that ‘infrasound’ is a generalized health problem for all people living near a wind turbine. It is something they cannot hear, but they can all feel it and that their health is at risk.

What we do need to note is that the turbine swish noise might be problematic for some people and when those affected by fluctuating sounds appear, we do need to pay attention. But if scores of people in an area start claiming that the blade swish sound is affecting them negatively – be skeptical. Intermittent sound fluctuation really only affects some very sensitive people – not everyone. It is a real problem – just not a really pervasive one.

For more on the infrasound and turbine issue, click here:
Infrasound from Wind Turbines – Fact, Fiction or Deception by Geoff Leventhall.

And click here for:
Do wind turbines produce significant low frequency sound levels?  by G.P. van den Berg

Click here for information on tubine noise assessments in other posts on my site:
A sound by any other name…

Special thanks to Appalachian State University for publishing the Leventhall and van den Berg papers in the Reports section of its very informative website.