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“for years, they have sheltered behind the mantra, now shown to be false, that has been presented repeatedly in many forms such as ‘What you can’t hear, can’t affect you.’ ”
6. Potential Protective Therapy Against Infrasound
A commonly-used clinical treatment could potentially solve the problem of clinical sensitivity to infrasound. Tympanosto- my tubes are small rubber “grommets” placed in a myringot- omy (small incision) in the tympanic membrane (eardrum) to keep the perforation open. They are routinely used in children to treat middle ear disease and have been used successfully
to treat cases of Ménière’s disease. Placement of tympanos- tomy tubes is a straightforward office procedure. Although tympanostomy tubes have negligible influence on hearing in speech frequencies, they drastically attenuate sensitivity to
low frequency sounds (Voss et al., 2001) by allowing pressure to equilibrate between the ear canal and the middle ear. The effective level of infrasound reaching the inner ear could be reduced by 40 dB or more by this treatment. Tympanostomy tubes are not permanent but typically extrude themselves after a period of months, or can be removed by the physician. No one has ever evaluated whether tympanostomy tubes alleviate the symptoms of those living near wind turbines. From the patient’s perspective, this may be preferable to moving out of their homes or using medical treatments for vertigo, nau-
sea, and/or sleep disturbance. The results of such treatment, whether positive, negative, would likely have considerable scientific influence on the wind turbine noise debate.
Conclusions and Concerns
We have described multiple ways in which infrasound and low-frequency sounds could affect the ear and give rise to the symptoms that some people living near wind turbines report. If, in time, the symptoms of those living near the turbines
are demonstrated to have a physiological basis, it will become apparent that the years of assertions from the wind industry’s acousticians that “what you can’t hear can’t affect you” or that symptoms are psychosomatic or a nocebo effect was a great injustice. The current highly-polarized situation has arisen
because our understanding of the consequences of long-term infrasound stimulation remains at a very primitive level. Based on well-established principles of the physiology of the ear and how it responds to very low-frequency sounds, there is ample justification to take this problem more seriously than it has been to date. There are many important scientific issues that can only be resolved through careful and objective research. Although infrasound generation in the laboratory is techni- cally difficult, some research groups are already in the process of designing the required equipment to perform controlled experiments in humans.
One area of concern is the role that some acousticians and societies of acousticians have played. The primary role of acousticians should be to protect and serve society from nega- tive influences of noise exposure. In the case of wind turbine noise, it appears that many have been failing in that role. For years, they have sheltered behind the mantra, now shown to be false, that has been presented repeatedly in many forms such as “What you can’t hear, can’t affect you.”; “If you cannot hear a sound you cannot perceive it in other ways and it does not affect you.”; “Infrasound from wind turbines is below the audible threshold and of no consequence.”; “Infrasound is negligible from this type of turbine.”; “I can state categorically that there is no significant infrasound from current designs of wind turbines.” All of these statements assume that hearing, derived from low-frequency-insensitive IHC responses, is the only mechanism by which low frequency sound can affect the body. We know this assumption is false and blame its origin on a lack of detailed understanding of the physiology of the ear.
Another concern that must be dealt with is the develop-
ment of wind turbine noise measurements that have clinical relevance. The use of A-weighting must be reassessed as it is based on insensitive, IHC-mediated hearing and grossly mis- represents inner ear stimulation generated by the noise. In the scientific domain, A-weighting sound measurements would be
26 | Acoustics Today | Winter 2014