I find this interesting because it sounds similar to the sound I hear on my 15" 2008 (July) Aluminum MacBook Pro. I'd describe the sound almost like a bug that was hitting a bug sized ping pong ball, like you say ...every minute or minute and a half or so.
I've heard this going on far longer than I can remember, but should note that I've had this logic board replaced not too long ago due to a sort of connection malfunction which caused the battery not to charge, eventually. I hear the sound before the replacement, and continue to hear it, but am not sure if it's an actual "problem" per say. It can be a bit of a nuisance if you don't tune it out, but other than that I'd be wary of calling it a major problem unless it is underlying a diagnostic sign of failure somewhere.
Can you link me to the Apple support thread where people are discussing this please ?
Doug