One person’s “noise” is another’s “music,” particularly when there is benefit generated by the source of the noise for one and not the other.
The issues regarding increases in the environmental noise levels of rural landscapes associated with electricity-generating wind turbines are complex.
On Monday, the county commissioners raise that allowable noise “limit” from 45-50 decibels.
The windmill industry had requested an allowable level of 55 decibels.
Environmental and industrial noise is typically measured with sound meters using one of two scales – dBA or dBC.
The dBA scale is less sensitive to lower pitched sounds for any given broad frequency noise. It would be a lower number than if the same noise is measured using the dBC scale, which is equally sensitive to lower, mid and higher frequencies.
Much of the “woosh” noise created by wind turbine propellers is low frequency. A dBC measure would be more appropriate to estimate the noise being generated by the rotating blades.
Standards should be established for noise generated at the base of the turbine, at the property line of rural residents and at the outer walls of the homes, particularly the outer walls of the house of those who do not have a financial interest in the power generation.
They will likely assess the effects of the noise differently than those who are financially benefitting from the windmills.
Most city noise ordinances have a stricter requirement for noise levels during the typical “sleeping” hours. The rural environment where these turbines are being built can be pretty noisy – tractors, trucks, combines, mowers, etc.
However, not all rural residents are farmers, and there are different expectations for those who have moved to the country for its “quiet solitude” than for farm families who are making their living from the work that is often the source of rural noise.
Clearly these two types of rural residents have different expectations and tolerances for noise during the working day.
However, both would probably agree that they expect relative quiet when they are trying to sleep with windows open at night.
The question that both groups should ask is whether the wind turbines can be stopped or silenced between 11 p.m. and 7 a.m so the turbines do not contribute to higher noise levels when people are trying to sleep? A reading of 50 decibels would not be acceptable for those attempting to sleep.
Those levels are not going to harm human hearing. However, these sound levels can be annoying, disturb sleep patterns, increase anxiety and annoyance levels, similar to a dripping faucet or a dog barking in the distance.
Now think about this kind of low-level noise 24 hours a day. As these wind turbines age, consider not only the “whoosh” of the turning blades, but also the addition of the “screech/rattle” of worn moving parts.
Although the generation of electrical power using wind has great potential to help release us from our dependence on fossil fuels, the undesirable environmental and human impact of the noise associated with these wind farms, must be proactively controlled at the source.
I suggest the following:
1. Use dBC scale to measure noise levels.
2. Specify acceptable noise levels as measured at the base of the turbine, at homeowners’ property lines, and ultimately their houses.
3. Define maintenance schedules for each turbine with associated requirements for annual noise level monitoring.
4. Consider turning the turbines off each day during sleeping hours.
5. Affected residents should purchase a relatively inexpensive sound level meter and determine current decibel levels in their areas at different times of the day before the turbines are installed.
A firm has recently been hired to do a sound level assessment and make policy recommendations. However, they will not necessarily measure the noise levels where you live.
Rural residents should take ownership of this debate and record their baseline noise levels that ideally should not be exceeded with the future development of adjacent wind farms.
Novak heads Purdue University’s Department of Speech, Language and Hearing Sciences.
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