Parking our longterm 2012 Volvo S60 in Edmunds Intergalactic Headquarters parking garage yesterday, I noticed a distinct groany noise that was vaguely reminiscent of the power steering in my first car.
That car, an '82 Olds Cutlass Supreme, had a perpetual power steering leak (among others) that at the time I was too poor to fix. Even finding gas money was like an easter egg hunt at each fuel stop. I'd search for loose change under the seats, carpet, in the trunk, jammed in the dash, etc. Back to the leak. Over time the power steering pump would develop a groan when you turned the wheel. That was how I gauged the fluid level, actually.
Anyway, memories. Our Volvo elicts them. I switched its a/c off and on to try to pinpoint the noise it made, and, sure enough, doing so made the groan come and go. It's not really the worrying kind of noise, but it is peculiar given how quiet modern cars usually are.
Jason Kavanagh, Engineering Editor

barich1 says:
06:35 AM, 02/14/12
The A/C in my Mazda3 is very loud. At idle, you hear a clunk and whoosh, followed by a groaning the entire time the compressor is on. The whoosh is so loud I can hear it while driving 25-30 MPH. When the compressor kicks in there's also a significant increase in engine vibration.
I really hope that Mazda switches or has switched to a variable compressor. I drove a VW with one and you couldn't tell from inside the car that the A/C had been turned on (other than the cold air, of course).
sethyt says:
09:18 AM, 02/14/12
I have a 2012 S60 T5 and I had also noticed this annoying noise. Interestingly enough, I also had the same memory association, except mine recalled early 90s Ford products' power steering pumps.
Other than this small issue, my S60 has been completely problem free. The S60 has definitely exceeded all of my expectations, and I am incredibly happy with my car.
I do intend to have this problem addressed by my dealer at the next service. This noise is not acceptable for a new $35k+ car. Thankfully, I have not had to listen to it much recently, as I do not turn on the A/C compressor during our DC winters.
esoterica says:
10:19 AM, 02/14/12
In Edmunds' grand tradition, this exact issue has been complained about before on this blog. Do you guys not also write this stuff down in problem logs for dealer visits?
cdp8 says:
02:04 PM, 02/14/12
It is typical of all Volvos of the past eight to ten years. On a 2005 V50 I used to own, it sounded like a very faint barking dog. On my current 2009 XC70 the noise is so faint that it can only be heard with the sound system off while stationary. Even minimal road noise drowns it out.
It is a damper cycling in the automatic climate control system. Trying running the system on manual. Pick a vent from the human pictogram, set a fan speed and the temp and the noise should disappear.
Look up barking dog on swedespeed.com. I think Volvo found a solution.