<H2> how noisy are wind turbines?
<H2> current approach to regulating wind farm noise
<H2> what some neighbors are hearing
<H2> possible factors in noise complaints
<H2> detailed documents of note
<H2> emerging technologies
<H2> wind energy advocates, pro and con
<H2> trade organizations
<H2> governmental entities
<H2> landowner support
<H2> wind advocacy organizations
<H2> wind turbine noise activists
<H3> variations in individual responses to wind farm noise
<H3> low-frequency noise
<H3> health effects
<H3> local regulatory challenges
<H3> predicted noise is unrealistically optimized
<H3> topographical effects
<H3> atmospheric effects
<b> noise impacts are not necessarily deal-killers for wind energy, as long as developers are honest about what is likely to be heard and continue to work diligently to investigate the aspects of wind turbine noise that are still not fully understood
<b> if the thousands of windfarms likely to be built in the coming decade are placed too close to homes, the industry will be faced with an echoing chorus of complaints and resistance for years to come, even if it manages to invent much quieter machines. better to be conservative, accepting the fact that even occasional atmospheric effects should be factored in to siting decisions today, so as to build a reservoir of good will, rather than a rising tide of complaints.
<b> note: this aei special report will be periodicaly updated, incorporating new research, more recent reports, and suggestions/comments from readers. several topics will be added over time, including: effects of noise on wildlife and habitat, offshore wind energy, and the health effects of chronic noise exposure.
<b> design of turbine blades is of course continually being improved; after all, the noise is a sign of inefficiency (rotational energy sacrificed by aerodynamic turbulence), so newer blades are likely to be quieter
<b> it should be noted that the majority of wind farms do not trigger noise complaints. these are likely sited far enough away to work well for nearby residents.
<b> it is important to measure the noise from turbines using a db(c) scale
<b> night time atmospheric stability
<b> with light and steady breezes capable of spinning the turbines, but not stirring up much ambient noise, sound levels measured at homes a half mile to nearly two miles away are often 5-15db higher than models would suggest.
<b> with current knowledge, the effects of stability on the wind profile over flat ground can be modelled satisfactorily. (his measurements indicate that more sophisticated sound models were accurate to within 1.5db)
<b> at the end of an intensive two-year period of studying the complexities of atmospheric turbulence and stability on wind turbine noise, g.p. van den berg offered this sage advice:
<b> a change in public relations can also make a difference: proponents must accept that wind turbine noise is not (always) lsquo;benignrsquo;, that the noise may affect people, and that people who are complaining are not always just a nuisance.
<b> official noise standards can very easily fail to protect nearby residents from disruptive levels of noise
<b> the sounds of high winds: the effect of atmospheric stability on wind turbine sound and microphone noise
<b> wind farm noise and regulations in the eastern united states
<b> how to guide to wind turbine siting
<b> wind turbines, noise, and health
<b> research into aerodynamic modulation of wind turbine noise: a final report
<b> amplitude modulation of wind turbine noise: a review of the evidence.
<b> who (world health organization) night noise guidelines
<b> these designs are sized for home, office building, or apartment building applications. none have been scaled for use in wind-farm settings
<b> carbon concepts
<strong>[download this report (33p pdf)]
<strong>please also see:
<strong>while about half the people who can hear wind turbines seem not to be particularly bothered by the noise, a substantial minority (around 25%) are more sensitive to the noise, often reporting serious sleep disturbance.
<strong>for more detailed consideration of some of these studies, see two posts at aeinews.org:
<strong>clearly, 35-45db is a range at which impacts on neighbors become far more widespread. the social question that will need to be addressed is what proportion of nearby neighbors we will accept causing sleep deprivation or annoyance in: 10%? 20%?
<strong>it is important for all concerned to not get overly caught up in the controversy over low-frequency noise
<strong>it is quite likely that most of the symptoms reported (irritability, increased blood pressure, headaches, poor concentration, etc.) are, in most cases, largely secondary effects of sleep disruption
<strong>world health organization in 2009 released a comprehensive report on the health effects of night time noise
<strong>wind turbine syndrome
<strong>(please see aei's comments on this work in the low frequency noise section, just above)
<strong> are we simply hearing from the most sensitive or the most crotchety people? a recent research paper suggests not.
<strongᡤ-50% of people under a half mile away were highly annoyed (over a third within a half mile had been awakened by turbine noise)
<strong>sleep disturbance and wind turbine noise
<strong>noise radiation from wind turbines installed near homes: effects on health
<strong>wind turbine noise biannual international conference
<strong>[wtn 2009 website]
<strong>wind turbine syndrome
<i>how big are modern wind turbines? the ones on the left are 60m and 125m; the one on the right is 95m, with blades sweeping an area the size of a 747.
<i>by and large, those affected by the noise generated by wind turbines live within a few miles of a large wind power plant or within several hundred feet of a small plant or individual turbine. although the noise at these distances is not great -- a 300-kilowatt (kw) turbine typically produces less noise at 400 feet than does light traffic 100 feet away -- it nevertheless is sufficient to be heard indoors and may be especially disturbing in the middle of the night when traffic and household sounds are diminished.
<i>two examples of a wind rose
<i>iowa state university center for agricultural law and taxation:
<i>ontario federation of agriculture:
<i>d'entremont family home, now abandoned
<i>disturbance from noise is undoubtedly subjective:
<i>on the other side of the subjective coin, from mars hill resident wendy todd (house is 2600 feet from the nearest turbine):
<i>two views of the mars hill wind farm, showing proximity of rural landowners. it is not hard to imagine noise blanketing the fields, especially when the hill is sheltering the lowlands from wind.
<i>(wendy todd, continued):
<i>note: a 2007 study in the uk, comparing modeled sound levels to measured sound levels, indicates that some models are more reliable predictors of sound transmission. specifically, the researchers found that when they used a conservative (worst-case) factor for ground hardness (and thus sound transmission) the actual recorded sound was nearly always lower than predicted at close and mid range (100m-500m), with a bit more variation and scattered higher measured sound at longer range (750m) . when using a mixed cover factor for ground cover, measured sound was more often louder than predicted, sometimes by as much as 5-7db (the mixed cover results were only reported at 750m).
<i>note: the same factors that can disrupt the idealized spherical spreading models, as noted above, also will tend to create a more chaotic pattern of sound waves from each turbine, thus also limiting the impact, and certainly the predictability, of coherence effects.
<i>the above sections draw on several detailed reports by others. those wishing to learn more, or to inform themselves so as to discuss these issues in depth with regulatory authorities, company representatives, acousticians, or neighbors, will benefit from reading the source material below.
<i>resources/advice for landowners signing lease and easement agreements with energy companies