Are the noises just in my head?

I started riding my first fixie in January. But I commute I mostly on an internal hub Nexus. For three days in a row I rode my fixie and then today the internal hub bike and I kept hearing some noise. I would pull over and everything checked out okay. But then I would ride and start hearing it again. It's not the freewheel clicking sound. It's a very slight brush rubbing on a cymbal sound.

Then I started to think it's just all in my head. That the sound has always been there and never noticed it until I started to ride a super quiet fixed gear. It's getting aggrevating pulling over again and again to find nothing wrong.

So I was wondering if any of you all have had a similar experience. Is there a problem with my bike or is there just another problem with my brain?