I had my front tires changed on 96 altima, and after few days I noticed
that I was hearing a periodic loud chirp (bird-like) noise from the
passenger side. The noise was most  prominant when the windows were
down and when going under a bridge or between closed spaces.

The pitch of the noise changed with the speed, and didnt seem to be
related to engine or brakes.

After a couple of days of reading posts online, I concluded it might be
time to spend some $$$ and get the possibly expensive fix.  Just out of
curiousity I inspected the tires and axels once more before taking the
car to a mechanic and found out what was making this noise. The
air-outlet on the right tire was brushing against the hub-cap (which
was not properly aligned). I just removed and put back the hub cap
properly and thats it.. it was that simple.

I thought I would post this just in case someone finds it useful...
sometimes simplest of things can drive someone nuts :)