Narrative:

On climbout at 28;000 feet to 30;000 feet MSL had a loud harmonic vibration at mid-cabin. Diverted to ZZZ.

Google
 

Original NASA ASRS Text

Title: A B737-300 climbing at FL280 to FL300 developed a loud harmonic vibration at mid-cabin so the crew diverted to a nearby airport.

Narrative: On climbout at 28;000 feet to 30;000 feet MSL had a loud harmonic vibration at mid-cabin. Diverted to ZZZ.

Data retrieved from NASA's ASRS site as of July 2013 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.