With a single fan, the Sonata lived up to its claims of whisper quiet function. Even with the addition of a second 120mm fan, the Sonata was still able to operate within a very tolerable level of noise (still more quiet than any case I've used in the past). The overal cooling performance of the enclosure was fairly decent. Compared to my previous case which used a total of (4) 80mm fans, the Sonata operated approximately 1-2C higher in temperature. Adding the 2nd 120mm fan pushed internal temperatures down that extra 1-2C.