I went to a field of windmills this morning at sunrise and as I got close to one of them, almost underneath it, I heard a very odd sound coming from the windmill. It sounded like the tearing sound of a log being split in half, almost a crackling sound. The wind was very minimal, only turning it about 2-6 rpm.
When I got home I watched/listened to videos that had sound from windmills (the same size and design) and they sounded very "wooshy" and smoother, nothing like I had heard in the morning. Is there any explanation to why I heard such a peculiar noise coming from the windmill? I also have a picture of one of the windmills for reference.