Machine louder?

At 3 a.m. this morning, my wife told me that my System One machine was louder than normal. By this she meant the Vader-like breathing sound, which had a bit of a wheeze sound to it. I turned it off and on, but it didn't fix it. I couldn't find anything unusual with the mask such as a leak or partially disengaged hose that might account for this. However, when I tried the machine after waking in the morning,its sound level seems normal.

Any thoughts on what can cause sound level changes like this?

Sounds more like a mask/leak problem. Also..check the hose for leaks.

That does sound like a leak somewhere, that may sound louder if your pressure is going up at that point. Perhaps you went into some stage of sleep where you need more pressure, so the sound was more noticeable? I've noticed with mine that it gets somewhat louder as I raise the humidity level too.

Thanks for the comments. SleepyHead shows that, in the 10 minutes before my wife's comment, there was a cluster of six hypopnea and clear airway events that caused the machine pressure to go up from its baseline of 6.5 to 8.5; the leak rate also showed as going up somewhat but not by a huge amount. I'll doublecheck the mask fit and look over the hose for leaks. Right now I've got the humidity level on 4, maybe I can try dropping it to 3.