I think I had the same sound.
I have tossed around whether or not to comment because I'm no mechanic, but I had a " ticking " or " rattle " around 3500 until 4000 that appeared at around 10,000 miles on my 2010 GSA. Sounded like it was coming up from beneath the instruments. I asked Max in Troy about it at my 12,000 mile service & it went in one ear and out the other, so I lived with the noise in hopes that it would disappear. But that little crap sure bugs me.
A few months back, ( around 16,000 miles ) a local gas station started selling Ethanol- free gas. I started running that fuel and the noise disappeared immediately. Gone. Prior to, I always gassed up (10% Ethanol) at pretty much the same couple of stations down the road from home. Now as I said, I 'aint no mechanic and I'm not a fuel expert, and perhaps it was just happenstance, but that gas seems to have stopped the noise. I have not heard it for the past 2,500 miles. Perhaps it was the quality of the fuel that I was using before the Ethanol free and not the Ethanol itself, I dont know. Maybe it had nothing to do with the fuel, but if you are not running Ethanol-free and have a chance to, give it a try. If you are running it, try changing things up with fuel from another station or two.
I'd be interested to hear if it makes a difference for anyone.