Air conditioning noise

I have A 2003 Subaru Outback wagon with exactly the same AC noise issue. The AC blows cold, and occasionally a low-pitched moaning sound (like a goose) is made appearing to come from under the dash. It also seems to get slightly more humid and a little warmer right after the noise is made, like the outside airvent has been opened. That clears up quickly and doesn't happen again until the noise repeats. The AC was just serviced, and the high-pressure hose replaced. Is it possible that the noise is caused by improper charging, or a vacuum hose leak?

I've had this problem from the very beginning. Bought the car in 2001 October (2002) Outback Limited. The sound began the first it warmed in May (I was living in DC). Took the car back a couple times. No one could hear it, had no idea, looked at me like I was some dope. Over the years I've gotten used to it, but still annoying. Especially if driving in traffic and suddenly it happens. Can almost be as loud as a horn. Also, embarrassing when it continues after the car is shut off. I doubt it is the compressor unless I had a crappy one from day one (The first time I took it in, the car had 3500 miles on it). Has there been any updates or service notes on this at all? Does anyone know?

Cecil, did you ever get an answer?

I have a 2002 Outback with the same problem. The moan is quite loud. I'm thinking it could possibly be the expansion valve vibrating when the compressor shuts off. Did you ever get a solution?

Any solution to this?