I found this to be true when I was using my PR machine without the humidifier attached. I took the humidifier unit off when running the machine on my power pack when out in our travel trailer a few weeks ago. My AHI numbers were better so I just left the humidifier off at home for a few nights, but I couldn't deal with the noise coming through the hose. I've decided not to use the heated hose or humidification for a longer trial period, but had to re-attach the humidifier--I do put water in it but no heat--and now back to quiet operation.
I like the AHI figures--now often under 1.0. My CA events have also dropped--not certain if this humidification change has anything to do with it.