Funny thing today.
I had to go out to a customer with two stacked MS225-48FP's which were the noisy ones to have them replaced under the proactive replacement program.
I came into the room with the closet and said, man! It's quiet in here compared to last time.
When opening the closet I noticed the fans had already failed but the switches were still running, but hotter than usual.
I could hear the fans slightly starting and directly stopping.
It went from an aeroplane to an old woman groaning sound.