New S9-Auto vs older S9-Auto

The new S9 seems to be louder than the the older one and my AHI is higher on the new machine and I think I think they are on the same settings.
Sleephead report from the new unit:
http://www.abnormal.com/cpap/s92-Jan-11.pdf
Sleepyhead report from the old unit:
http://www.abnormal.com/cpap/s91.jan.10.pdf
Can anyone tell me if I missed a setting?

The pressure curve is much different as the the low pressure of the first one stays at about 4 while the new one follows the trends on the higher pressure.

The new one seems to purr when I exhale while the older one didn't. The sound meter says they are the same but my ear says the new one is louder. I'm using the same mask and tube.

There are some differences between the machines and it seems mostly cosmetic. The older on is an S9-AutoSet with "easy breathe" and the new one is "S9-AutoSet" with "EPR" if that matters. The new one is made in Singapore while the rental I now need to return was made in Australia. The older one has the stickers for the Aussie market and the other one has stickers for the US market.

If there's a difference in the exhalation relief, that could be what you are hearing. This would make sense, especially since you say that there isn't technically a difference in the noise the two machines make. I know that my machine seems quieter when I turn of the exhalation relief, because it runs at a steady pressure and there's no variation in sound. With the relief, it changes pressure with each breath, and the variation in the sound make it more noticeable.

So, where are the new Respironics automatic machines made?
Just curious.

I dropped the ERP setting back to "off" and that helps with the noise but its still louder than the older unit. I wonder if they don't balance the motors as well as they used to.