Overhead Speaker???

2003 Chevy Silverado Z71, has a little (2inch) speaker grill in the headliner directly above drivers head, left ear ...... It sometimes wines, and after I shut off truck, it slowly winds down and then stops...... WHAT is that ?? A speaker and for what ??????

If the grill you are looking at is on the left side of your head that is part of your automatic climate control. That piece takes in air.

Thanks much for that ..... so I guess my fan that is sucking in air, is going out?????? You got a name/part number for that ???

FOUND IT - it is called an ASPIRATOR P/N: 25771194 ...... $45 at GMpartsdirect.com

Does anybody know how I can "SHUT IT UP" and if there are any replace procedures for it???