well, if you open on your glove box you will notice two little black circles on each side (like tabs)
if you undo them, your glove box will fall open and you can look behind there.
You will see all the climate control duct work back in there, and thats where the sound came from.
If you are allergic to stuff, get a hypo-algergentic house Air Filter
and stick that in this area, you will notice a HUGE difference!
link to do this: https://www.celicahobby.com/ubbthreads/thread.f_57102_0_collapsed_2__1.html
If you need better pics, I can take you some when I get home!