Currently Being ModeratedFeb 14, 2013 7:39 AM (in response to RBandres)
Try cleaning the microphone hole at the top center back (opposite the Home button). Make sure your case (if any) or your fingers are not obstructing.
A restart or reset might help:
Restart: Press On/Off button until the Slide to Power Off slider appears, select Slide to Power Off and, after the iPad shuts down, then press the On/Off button until the Apple logo appears.
Reset: Press the Home and On/Off buttons at the same time and hold them until the Apple logo appears (about 10 seconds). Ignore the "Slide to power off"
If the hardware is broken you will have to contact Apple Support or visit an Apple store.