The biggest issue is whether or not site locations have low level wind shear occur across the area of the blade rotation. If the answer is yes, then the blade moving through the slow or dead air is the biggest culprit in making noise. (It's pushing air rather than being pushed by air, and it is not designed for that.) It's tricky because the phenomena varies on a site-by-site basis. Some locations practically never have it happen, others it may be seasonal (prevailing winds changing direction and interacting with landscape features) or even frequent. That is why there are differing arguments over whether this form of clean energy generation makes for a good neighbor. Although it's good to try and address the general low level noise with expected operation, there are conditions for potential blade noise that would have to be looked at with long term surveys and modeling in planned locations. And that is a more challenging problem to solve.