Why do travel CPAPs make so much noise at the mask? 

  
I have a Resmed Airsense 11.  Almost silent under normal use.  But the Resmed Airmini makes the devil's own noise.  Same mask, same settings, the Resmed Airmini causes a roar to come out at the mask elbow.  In a comment I'll upload an A-B test video so you can hear for yourself.  

I posted this issue before when I tried a Transcend Micro (which I returned).  So loud I had to wear earplugs.  The noise was coming from the mask elbow, but when I asked about it then, everyone was gaslighting me saying the noise was from the unit when I could clearly hear it coming from the mask itself. I added a muffler, no help it still roared.  I returned the Transcend travel unit.

  
Resmend Airmini uses the same fan and motor, the same electronics as the Airsense 11, just skips the water chamber and the screen.  The big unit doesn't make much noise at all.  

Could the problem be turbulence with the smaller unit, which (a theory) be smoothed out by the muffler action of the water chamber in the big brother?  Do mufflers help this issue?  

So far the Airmini travel CPAP looks like a waste of 900 smackeroons. 

Travel CPAPs always noisy