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Regarding the whining noise with the S9. I know I initially said I love the machine but mine has been bothering me a lot the last few nights. I tend to sleep on my side or stomach and the whining noise comes right through the mattress even though the machine is under the bed. It is higher pitched when I breath in and lower when I breath out.

I have tried increasing the base pressure, lowing the pressure, setting a straight pressure but nothing makes much difference.

What I have noticed, however, is that when I wake up in the morning, there is no whine, just a level white noise which does not bother me at all. Anyone have any ideas about this? Does the machine need time to evaluate breathing for some time and during that time it whines? It's just a thought.

I took a look to see what the pressure was at in the morning through the software, since I have the machine set to auto. It was at 9.48 but when I have set the machine to an even 10 and not on auto, I still hear the whine. It seems odd to me. Is this a bad machine or are they all like this? Granted it is not that loud but that noise like wind rushing past a crack in the door is very annoying.

The issue here is that the machine is not supposed to whine. Some people report absolutely quiet machines, while others, such as myself have a distinct whining sound that comes from the blower unit (not the humidifier). It sounds like an air whistling or gear whining noise during exhalation. Inhalation is absolutely quiet.

The fact that some machines are making this noise is probably related to certain manufacturing tolerances out of whack... Q.C. probably slipped a bit.

My machine says it was manufactured in Australia, I dont have the exact date, but I recall that it was fairly recent.

In any event, my DME got Resmed to send out another brand new unit with no questions asked. I will get it tomorrow and report my findings.

Seems to me that Resmed knows they have a problem with the noise. I mean , that is one of their biggest selling points after all... and its the one they are not delivering.

Otherwise, everything about the machine is awesome (except the whine)