Some observations about the different measurements used in community noise. For the last 40 years, measurements of facilities have been either A-weighted or in bands: octave or ⅓-octave. These measurements were originally limited by the technology available in the instrumentation. The A-weighted curve approximates the human ear’s response at 40 dB over the audible frequency range. Sounds heard are not “masked” unless the sounds fall within the ear’s critical bands. Those bands are on the order of the ⅓-octave. Therefore, unless the intruding sounds are in the same critical bands as the background sounds, the facility will be heard.
Planners and governmental officials like to have a “budget” that can be used for approving or denying projects. Unfortunately, the human being does not act as an adding machine for sound, where you can get to “too much.” Each person hears the components of the environment and will know where each individual sound is coming from. In the case of internal combustion engines, it is possible to not know whether the engine is a distant car, airplane, or something else. As the sound source gets closer, a identification can often be made. The budget approach has been successfully used for hearing loss in workplaces. In the case of community projects, the equivalent level (Leq) or the day-night Aweighted equivalent level (DNL), used in transportation projects, has a disconnect with the levels observed by the people impacted by the sounds from the project. One concern is the statement about the percentage of highly annoyed residents. There seems to be a tacit assumption that some percentage of residents can be permitted to be highly annoyed by a project. What if this small percentage turns out to be those who are physically disposed to some disease, such as motion sickness? Are they to be “thrown under the bus” because they are highly annoyed about it? The percentage which was used for aircraft in the 1970s was 15% highly annoyed. Has anyone ever talked to these people about why they are highly annoyed? If those people have to move out of their homes because of the noise, will the project or the government compensate them? Probably not. It will be: “Too bad for you,” which will just make them more upset.
In the case of wind turbines, their sound is, apparently, very distinctive. In addition, in some cases, the blade passing frequency is in a range where the walls of a home do not attenuate the sound, and where symptoms of seasickness are prevalent.
Other Problems, Including Noise
In a recent Wall Street Journal editorial11, Jay Lehr makes the following observations about some of the lesser-known problems with wind turbines:
So, you might wonder, do high winds make turbines really hum? No. Turbines must be shut down in high winds because centrifugal force would begin to tear the blades apart. Also, the world has learned from experience in Europe — whose wind sculpture gardens may one day dwarf ours — that a one-millimeter buildup of bugs on the blades reduces their power output by as much as 25%.
There are other problems. Thousands of turbine breakdowns and accidents have been reported in recent years. The basic concrete foundations are suffering from strains, as reported by industry sources and on the wind-farm construction website windfardbop.com.
And there are environmental factors. Annoyingly, low-frequency noise produced by wind turbines, particularly large turbines, is driving some people away from their homes, according to numerous press reports. (Low-frequency noise regulations are already in place in Denmark while the phenomenon is the subject of continuing research.)
The Audubon Society now estimates bird deaths from turbines exceed a million per year …” Elsewhere it has been reported that some of those bird deaths are endangered species such as the American bald eagle.
This article has reviewed information on wind turbine noise which is familiar to the author. The information was from studies in the United States and abroad. The most recent information was all land-based. Despite reassurances by the developers of wind farms and the industry, there is evidence to support the existence of a health problem under some conditions and for some people with wind turbines, which appears to be tied to the infrasound or low frequency portion of the acoustic emissions of the turbine. It is important for scientists and engineers to acknowledge the problem and to work to eliminate it for affected residents who were the industry’s supporters. It is unfortunate that many of the affected citizens feel disenfranchised by their governments in response to this issue.