Flight Crew Air Transport Pilot (ATP)
Distraction
Aircraft Equipment Problem Critical
Flight Crew Diverted
Aircraft
On climbout at 28;000 feet to 30;000 feet MSL had a loud harmonic vibration at mid-cabin.  Diverted to ZZZ.
A B737-300 climbing at FL280 to FL300 developed a loud harmonic vibration at mid-cabin so the crew diverted to a nearby airport.