What you can’t hear can’t hurt you?

Geoff Leventhall (among others) is an acoustician with a long history of denying that infrasound (noise less than roughly 20hz) from wind turbines has any health effect on humans.  The basis of his belief seems to be that since you can’t “hear” these sounds they can’t possibly affect you.  As a example of his beliefs you only have to look at the AWEA/CanWEA Expert Panel Review, of which he was a member.  This is roughly equivalent to a physicist (not a physician) claiming you can’t be harmed by radiation that you can’t “see”.  Finally, one Dr. Alec Salt, a research member of the faculty of the Department of Otolaryngology (the ENT people) at Washington University’s School of Medicine took exception to this belief with this pretty terse statement: “The commonly held belief that low frequency sounds you cannot hear cannot affect the inner ear is incorrect.” [his emphasis]  Not much room to wiggle there.

From all appearances, Dr. Salt is no lightweight.  Educated in England, he has his share of grants, publications and awards to his credit.  His institution, Washington University in St. Louis, is also formidable.  His main interest seems to be the structure of the inner ear and how it reacts with drugs.  If there’s anyone more qualified to make the above statement it isn’t obvious who it would be.

He has a web page that introduces us to his very detailed report, which is soon to be published.  The introduction is suitable for a layperson like me, and builds the good case for his opinion.  The full report, titled Responses of the Ear to Infrasound and Wind Turbines, goes into exactly how he obtained his results.  I have a copy of the draft report and it is way beyond my ability to understand it.  From the full report:

The main points of our analysis can be summarized as follows:
1) Hearing perception, mediated by the inner hair cells of the cochlea, is remarkably insensitive to infrasound.
2) Other sensory cells or structures in the inner ear, such as the outer hair cells, are more sensitive to infrasound than the inner hair cells and can be stimulated by low frequency sounds at levels below those that are heard. The concept that an infrasonic sound that cannot be heard can have no influence on inner ear physiology is incorrect.
3) Under some clinical conditions, such as Meniere’s disease, superior canal dehiscence, or even asymptomatic cases of endolymphatic hydrops, individuals may be hypersensitive to infrasound.
4) A-weighting wind turbine sounds underestimates the likely influence of the sound on the ear. A greater effort should be made to document the infrasound component of wind turbine sounds under different conditions.
5) Based on our understanding of how low frequency sound is processed in the ear, and on reports indicating that wind turbine noise causes greater annoyance than other sounds of similar level and affects the quality of life in sensitive individuals, there is an urgent need for more research directly addressing the physiologic consequences of long-term, low level infrasound exposures on humans.

If Salt is correct and Leventhall’s presumption about inaudibility equaling no effects is incorrect this puts into question pretty much everything Leventhall has written over the last 10 years or so along with every paper written that depended upon him being correct.  Which is to say, every paper the wind industry has produced claiming there’s no health effects from wind turbines.

UPDATE, July 29, 2010

There was an article published in the NIH-NIDCD  that provides more details on Dr. Salt’s research.

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