Is my MacBook Pro Retina fan failing?

My MacBook Pro Retina 15" (Mid 2012) has what sounds like a failing sound. I've uploaded a recording to Dropbox however it's hard to hear.

The best I can describe the sound is that it sounds as if the fan is vibrating more then usual. There's a sort of buzz coming from it.

I know the best bet is to take the laptop to an Apple shop, but the closest one to me is an hour away, so wanted to make sure. Also, it still is under warranty, but without hearing the noise, what other tests can be done to check if it functions properly?

(Also, the battery needs replacing, which was confirmed by the Apple Store. When that is done, are the same fans put back in? I'm not sure what's glued to what inside).

Solution 1:

If they are replacing the battery and it is under warranty, just tell them the fan is buzzing and they will look at it while replacing the battery. It may just be something got in there and it's clanking around which could be solved by compressed air, but it could be failing.