Being new to CPAP, I was having trouble adjusting.  My "auto-titrator" variable pressure machine would hum or moan when I inhaled, and the manufacturer's technician said his did the same.  It then started waking me up with higher than normal pressure, making it hard for me to exhale, and causeing whistling leaks.  This would sometimes occur even before I would go to sleep; I would sharply inhale, and all of a sudden the machine would ramp up and start trying to give me emergency CPR.  The DME tech tried reprogrammin a lower pressure and asked me to try to get used to it.  I consulted with the manufacturer, who said it was either me, or that some electronic parts had to be reset.

I was getting frustrated and sleeping worse than before CPAP!  Finally, after exhausting all options, they gave me a replacement unit.  It is very quiet, and has yet to go berserk on me!  I don't want to suggest that everyone with issues has a defective machine, but apparently it is possible,a nd I thought others might want to know.

Russell