I posted a note about the voltage offset in the Avalon 8 official specs thread (https://bitcointalk.org/index.php?topic=2616205.msg30730555#new).
It looks like the values for voltage offset enter on the CGMiner Configuration page are being ignored and the offset and some other settings are getting applied to the command line of the cgminer.  
Try entering a value there other than zero and look in Processes - at the bottom of the list you should see the cgminer command line and it always has offset of 0 hardcoded.  It looks like we can override if we use "More Options" with "--avalon8-voltage-level-offset -2" (figured that out by taking akadamson suggestion and then finding the developer documentation for cgminer on Canaan's github.

For those who don't know or are new to this, the command line options can be found here (just look for the avalon7 options and maybe the options for avalon8 will be similar):  https://github.com/Canaan-Creative/cgminer/blob/master/README

So far it is running around 80% fan speed (it was 100% before) with chip temp at 67 C.  The hash rate is staying between 10.5 -10.8TH - with the offset of 0, it was 11.2-11.5TH.
Overall it is much quieter.

I don't have a way to test the power usage so if someone else does, it would be a good thing to test.