How to design a filter with a certain magnitude response
if you are only interested in designing a signal representing the wind turbine noise, you could just generate it from your magnitude. E.g., with your magnitude $A$ over frequency $f$ you can generate a random phase $\phi$ for each frequency and over a time $t$ and then add all together. Here a small code for illustration (I tried to use your varibles. However you need to check orientation etc.):

phi         = rand(size(fmag))*2*pi;
x           = (mag*sin(2*pi*fmag*t+repmat(phi,1,N)));


Hope this helps.