Measured 3 feet from the fan with it running, we showed readings of 74~75 db. Please understand that in this configuration the switching noise is absent so the unit will be a bit louder in the field. To closer replicate our test, the customer can temporarily set the IPPT Max % to 0%. this will reduce the sound of the IBGTs switching. The fan itself does not give off much noise considering it's size, but if the customer has a bad bearing or if the rubber isolators have broken down, it will be louder. A bad bearing should be easily detected just by listening to it.