The first troubleshooting step is to issue the "show chassis and show log" commands to check the current speed, temperature and if there is any error reported,if this is high issue the "show cpu " command 3 times to check if the cpu is high or low, if high, troubleshoot what ́s causing it, for example; a loop in the network, if the cpu is low, with the show version command look for if you have the right boot code that match 8070b (mnz10111.bin) Finally if there is no reason for noisy fans according to the results from the show commands is possible that you are facing a hardware issue so the last recommendation is open a ticket.
Thanks
Jose Fonseca
Technical Support Engineer II
Ruckus Networks, an ARRIS company