fan noise

Would an 8 inch fan be enough for 2 - 2x4 tents? Both are using Spider Farmer SF4000's. I'm worried about noise but I can deal with it to bring temps down from the mid 80's.

While looking for Db information on various fans available I stumbled across these tests on youtube. Tested by hydromag under the same conditions. Various tests including Db , airflow and power consumption with each fan under different conditions. 1m of ducting with no filter Filter and 4m of...