Wind turbines are moving a lot faster than they appear. E.g. Vestas v164 [1] rotates only at max 12 times per minute so looks slow. But because it has 80m blades, the tip speed is up to 100 meters per second (230mph). That's 1/3rd the speed of sound! That can generate a lot of noise.

[1] https://en.wind-turbine-models.com/turbines/1419-mhi-vestas-...