DS560 noticeably louder than DS220??

I received a PR System One REMStar 60 Series SE CPAP Machine (DS220) from my DME just a little over 2 months ago. I realized a bit too late that I got stuck with a "brick".

So that I could have full data I just bought a PR System One REMStar 60 Series Auto CPAP Machine (DS560) from our host (totally at my own expense). I received it today and I'm amazed at all the added features!

One thing that surprised me though is that the DS560 is noticeably louder than the DS220. The DS220 was set to a constant pressure of 10. I could pull my mask off and lay the hose down with it still running and could barely hear it. The DS560 is set to minimum pressure of 8 and a maximum pressure of 20. So far, it has never gone above 8. If I take the mask off and lay the hose down with it still running it is really loud. (It isn't nearly as noisy once I put the mask on.)

Is it normal that the DS560 should sound so much louder than the DS220? Or might there be something wrong with my machine?

I've had a 560 for 6 months and yes, it is noisy when running "wide open." (I've also measured the current draw, and its about triple its normal usage, so its certainly doing some work.) I've always taken this as a good sign, that the machine has plenty of reserve power, but it would be nice if it recognized it faster and did an automatic shutoff. I can only guess that the 220 is not designed to quickly ramp up the air volume like the 560 does.

In normal operation, its virtually silent, although I've managed to get a buzz a few times if its touching something that can vibrate.