mine are set to 45% on the modual3, but when it goes zombie or loses connection, the fans kicks into high speed, and its heard at the other end of the house..
if the fans loses the PMW signal, the controller will give it full juice, for safety..
By spec, if the PWM line is not connected the fan goes to 100% - has nothing to do with the controller.
Personally, I don't see the point of running the fans at less than max - keeps the unit cooler for better longevity - but noise isn't an issue for me.
By multiple reports, there ARE PWM fans out there that do NOT follow the spec, be sure to check your fans before you trust them to go 100% with no input to the PWM line.
from multiple cleaning teardowns, the PMW pin has worked itself loose out of one of the plug (retainer clip on the wire broke off), i have to manually push it in after plugging in the fan.
without any commands other then its preset fan speed, it is 100%, once cgminer tells it to go 45%, it then changes. when cgminer cannot talk to the avalon, the avalon goes back to 100% fan speed.