[horndoctor]

Wirelessly posted (htc Pocket PC: Mozilla/4.0 (compatible; MSIE 6.0; Windows CE; IEMobile 8.12; MSIEMobile6.0) Sprint T7380)

Sounds like something has broken loose and is vibrating sympathetically with the vibrator motor. Try activating the vibrator motor by calling your device while it's set to vibrate on ring and touching different parts on the device to see if you can find what is vibrating causing the noise. Try it with the keyboard open and closed. Hopefully it's something on the outside otherwise it's inside and that means you'll need to try to open it up yourself or take it in and get it repaired or replaced.