hmmm yeah that's the thing, I never really opened my routers for warranty purposes
unlike you might expect, the fan controller I have has really low power fans. it has been running over 3 years now 24/7 and I never cleaned it.
Still... the sound is lower than my WD mybook 1TB
I placed another drive on it as well... since it can become pretty hot... 50 degrees or something. It's an old drive, but with the laptop cooler it stays nicely around 30 degrees