I'm not sure about the Auto/C-Flex, but I know for a certainty that the Auto/A-Flex is much quieter than my old CPAP/C-Flex. It's so much quieter that a couple of times I've pulled my nasal pillows away from my face to make sure it was still on. By the way, I got my Auto/A-Flex from BestCPAPprice.co...

I'm a first time poster here though I've lurked in the forums as a Guest for quite some time. I've found the discussions and the suggestions to be very helpful. I had to post though to say that I wasn't using my CPAP with C-Flex because I couldn't stand the feeling of air being forced down my throat...