small speakers in front windshield area

[BOISE STATE FAN]

I have read through the owners manual to find my answer and had no luck. I recently purchased a 2003 Silverado and am curious as to what the small speaker like units are in the front windshield area and above the drivers head are. I realize this is probably common knowledge stuff but I can't seem to find anyone that knows what they are. Anyone else have the answer I am looking for? Any help would be greatly appreciated.

[01silverado2500]

The 2 small speaers by the windowsheild are the tweaters for the radio. If you lean forward with the radio on you can hear all the high notes comming from them.

 

The small circle above the driver's seat is the interior temp sensor for the auto climate control. There is a small fan inside it that pulls the inside air past a sensor and tells the auto climate control what to do.