Since no one else has answered, I will jump in with what little I know. I have a double oven but my top unit is a convection/microwave. You seem to have already answered your question about the larger louder fan. KA has had issues with self cleaning overheating/failures. The extra circulation is obviously there to keep the electronics cool. My unit is not very loud and I would think doubling it would not bother me. I wonder if there was something slightly loose and vibrating.

I also looked up your oven and as far as I could tell, both ovens have regular function. For one thing, it would be silly not to be able to turn a convection fan off.

I agree that not being able to turn off the convect fan in the bake mode is just plain silly, but that is the way this particular model works. The noise problem isn't that something is loose -- we have had an authorized service man out twice and it is the fan/air noise, not anything rattling. I've talked to the Whirlpool people and it seems that the convect fan issue is really planned into some of their units. I think it's ridiculous and I hope they carefully identify that this is the case. Some people may not care, but I wanted a clear choice between bake and convect.

Other than that, though, these ovens were just too noisy to keep and KitchenAid has agreed to take them back.

Ruthwebb1, when you say that "KitchenAid has agreed to take them back," where is that stated or printed? I have had techs out to fix mine multiple times, and it's still driving me nuts bc the cooling fan actually vibrates (besides the convection fan going).