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Some folks have it and some folks don't. It can sometimes be cured by making sure the hose attachment clicks well into place at the top of the machine, or can sometimes be alleviated by using electrical tape around a leaky hose or connection, or muffled with some other creative solution.
This assumes the humidifier attachment is there, even if not turned on, as the machine without it is stand-alone noisy.
Last night, after months of trouble-free, quiet use, my DreamStation started making the oft-described whirring motor noise. Why? What was the variable?
Well, I had overfilled the humidifier tub before putting it into the machine. Some water had spilled out of the internal tube-like structure located at about the halfway mark inside the tub. I had cleaned up the spill, but still put the rather overfilled tub into the machine. When I started the DreamStation, the whirring/whining began.
This could not do. I wiggled the hose connection to make sure it was well seated. I checked the hose for a crack or a leak. I turned the machine off and back on (hoping that like for a computer, sometimes a simple reboot will cure what ails it). All to no avail.
Then I removed the humidifier tub, emptied it into the sink so that the water level was back down to the actual RTFM-indicated level, then used a few tissues to sop up the excess water in the inner tube-like structure in the tub, sopped up the water that had spilled into the base of the machine below the tub and around the heating plate, and for good measure sopped up the rectangular rubber seal edges all along the inner lid of the humidifier chamber.
It worked. No more noise. I don't know which one of the above measures did the trick or whether it was a combination of some or all of them, but I postulate that the key is don't overfill the humidifier tub, and make sure if you do that you sop up any spilled water and keep the seals water-free. That should keep the old girl quiet.
HTH. YMMV.