karlog22, welcome to SF.
The top fan is the PSU fan and it's spinning either for high load or high temps. Looking at the dust build up I would hit the intake fans, mobo, and PSU with compressed air. I suspect that a high amount of dust is creating the noise as the PSU fan is working to cool. Oh and the rear case fans are in push/pull arrangement. Do you have a front mounted intake fan and or how and where is the cool air coming into the case?