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<br />4. Sound: <br /> <br />Modern wind turbines have better <br />insulation, lower rotation speeds, fewer <br />moving parts, no gearboxes, and more <br />efficient blades that make them much <br />quieter than their ancestors. Today's <br />turbines emit sound that is barely <br />discernible from ambient noise, even <br />with a decibel (dB) meter. Sound from <br />traffic, rustling trees, airplanes, and <br />people in fact often sufficiently mask <br />the dull, low, "white noise" sounds a <br />small turbine can make at certain wind <br />speeds. Only during short-term events <br />like severe storms or utility outages do <br />turbines make distinctive sounds, but in <br />these occurrences ambient sound levels <br />increase as well. <br /> <br />To put this into further perspective, <br />the sound made.by the lanyard clasp <br />on a flagpole line hitting its pole is far <br />more "tonal" and distinguishable than <br />any sound a small wind turbine makes, <br />and is less easily masked by ambient <br />sounds.6 <br /> <br />Zoning policy should reflect al1Jbient <br />sound levels as well as occasions. <br />where no affected parties are located <br />immediately outside a property <br />boundary. Therefore, except during <br />short-term events like storms and utility <br />outages, a small wind system should be <br />installed and operated such that sound <br />pressure levels do not exceed the <br />definition of "nuisance noise" as <br />established by existing zoning code. <br />or at the nearest dwelling, whichever <br />is greater. Sound levels should always <br />be measured downwind of the turbine <br />to account for the canceling effect of <br />the sound of the wind itself. If ambient <br />sound levels exceed "nuisance" levels <br /> <br />on certain occasions, such as during <br />storms, sound level limits of smallwind <br />systems should also be given reprieve <br />during these events which are out of <br />everyone's control. <br /> <br />Or, instead of singling out wind turbines <br />in sound regulations, it may be more <br />fair and administratively simple to use <br />default sound/noise regulations that <br />apply universally to other objects and <br />appliances in a community. The small <br />wind section of Wisconsin's (state-wide) <br />zoning ordinance, for example, has no <br />mention of sound because its designers <br />chose to treat small wind turbines <br />equally with other allowed <br />d evices/ structu res. <br /> <br /> <br />Sound Level Comparison <br /> <br />Modern small <br />wind turbines are <br />typically quieter <br />than most external <br />air conditioners. <br /> <br /> <br />A clasp hitting a flagpole <br />is far more distinguishable <br />than any sound a small <br />wind turbine makes <br /> <br /> <br />6 Flag clasp photo credits: <br />Flags Unlimited <br /> <br />