If the wind blows from the observer to the source,f2>f1
If the wind blows from the source to the observerf2<f1.
If the wind blows from the source to the observer,f2>f1
If the wind blows from observer to the source,f2<f1
If wind blows from source to observer
f2 = f1(V + w + u)/(V + w - u)
When wind blows from observer towards source
f2 = f1(V - w + u)/(V - w - u)
In both cases, f2 > f1