Friday December 3, 1614 Hrs.- The FAA Control Tower at Boston's Logan International Airport notified the Massport Fire/Rescue Dept.(Crew 1) of a Delta B737 returning to land with a vibration type noise in the rear of the aircraft. There was 111 passengers including crew on board. At 1645 Hrs., the A/C landed on Runway 22L with the fire dept. apparatus following the aircraft down the runway. The aircraft landed without incident and the Captain of the aircraft reported no steering problems while taxiing into the gate. The Delta B737 was heading to Ft. Myers, FL. from Boston and returned when the Capt. of the plane heard the noise and decleared an emergency. No injuries reported.