Stuart, I've heard this A/C with the fresh air option ON, and it was pretty quiet. I've heard normal A/C's without ventilation being a lot louder than this.
It's the model I'm going to use for my studio. (2 of them)
Although I will have a seperate ventilation system...

The reason I'm going to get this is for it's supposedly "Good Air purification and Humidity Control"
I was thinking of using it as a ventilation system as well, but went with the "typical fan-silencer" alternative.
This only brings air in, it doesn't take it out as well.
I suppose you would also require an exit route for the air if you use this. So you would have also a hole with silencer?
cheers