Good point, I thought it was from the brake when I first heard this noise.When driving around in any parking deck with the windows open, I hear all sorts of noises from the car, some like this. I also hear squeeks and squeals from the calipers slightly rubbing against the rotors. I've concluded that because the car it so quiet. You can pick out these noises. Most ice vehicles have an engine running which tends to drown out these noises.
However, what made me concerned are: the car makes this noise in random time, and the noise itself is random. For example, it sometimes makes "tic --- tic -tic" and sometimes "tititititic" "tictic." I would think that if the noise is coming from mechanical parts, it should, at least, have consistency. Furthermore, my Volt only has about 30,000 miles, and this noise started recently.
Noise is not loud; however, when the window is down, it is discernible. I recorded this video in a parking deck, just because my phone would pick up sound better in a quiet place like a parking deck.