Riding in to work this morning I started hearing some rattling coming from the area of the front wheel. I was able to make the noise louder by swerving side to side. I just got some downtime at work so I flipped the bike over, removed, and reseated the wheel. When I spin the wheel by hand I hear a very faint ticking noise, but it doesn't look to me like the spokes are hitting anything. The brake cable is released so the rim is not hitting the pads or anything.

The ticking isn't regular as in once or twice per revolution, rather it occurs with the frequency of poppoing pop corn kernels in the microwave. 2 or three clicks per revolution.

Any idea what my problem could be? Something in the hub? In the spokes? Is the faint sound I hear while having the bike upside down even related the rattling noise I hear when riding?

Any help is appreciated!