Setback distances are meant to mitigate the impacts of sound and shadows caused by blades passing. Local or state ordinances/permits sometimes include more specific provisions related to sound level and shadow flicker.
Individuals have a wide range of varied reactions to sound of all kinds, including wind turbine sound. That means it is extremely difficult to pinpoint a particular sound level (or decibel measurement) as being universally the “right” level.
Wind developers take great care to ensure that projects are sited in a way that makes sound at neighboring residences lower than would typically be noticeable. This is done through advanced and very accurate computer modeling technology, a long history of operational experience, and good common sense. The care taken to properly site turbines is evidenced in the millions of people that live near wind farms without issue. In fact, as of 2015, more than 1.3 million homes are within five miles of a utility-scale wind turbine, according to the Lawrence Berkley National Laboratory (LBNL). According to the same LBNL study, 92 percent of people living within five miles of a wind farm report positive or neutral experiences.
It helps that wind turbines sound is extremely low. Most people that visit operating wind projects are amazed at how quiet they are. Typically, two people can carry on a conversation at normal voice levels even while standing directly below a turbine, and the sound of the wind itself is often far more noticeable than the sound of the turbine.
Shadow flicker permitting
Shadow flicker describes the shadows cast by moving wind turbine blades on sunny days. Shadow flicker analysis is performed through computer-based mapping and modeling and is highly predictable. General setback requirements are typically enough to mitigate the shadow flicker annoyance. However, some jurisdictions choose to separately regulate shadow flicker. For example, an ordinance could limit shadow flicker to nonparticipating occupied buildings to a set number of hours per year.
Shadow flicker, when it does occur, typically lasts just a few minutes near sunrise or sunset and only occurs at certain times of the year, as it’s dependent on the sun’s angle. Is most cases it is also easily mitigated.
Positive effects of wind energy
Consideration of any potential health effects related to wind turbine sound should always include the benefits of wind energy for the environment and public health. Wind energy is an inexhaustible resource that generates no pollution or hazardous waste. It does not deplete fresh water resources, and requires no mining for fuel, transportation, or refining of a feedstock or fuel. Further, electricity produced by wind farms displaces electricity from other sources. Wind power thus has a direct and immediate benefit to health impacts associated with air pollution, such as asthma. In fact, wind has created billions of dollars in public health savings by cutting pollution that creates smog and triggers asthma attacks.