Any question answered...

I rode my road bike in today and noticed a rhythmic brushing noise from the front brake, only when using it. It makes a tttthhhhhttt noise, not a clunk, exactly once every wheel rotation. I checked the rim and tire and there's no scratch, seam, etc. Doesn't seem to be anything stuck in the pad - and anyway, it occurs on a wheel rotation, so I'd have thought it was rim/tyre. Any ideas?

Rim seam/join slightly raised? Often after rim+pothole meeting.
Worn rims, about to split (my fave).
Buckle - easy fixed.

Pad could be rubbing on tyre too if they're close and not quite adjusted right. Could also be your ears reaching resonance velocity..