Active control of single-frequency interior noise in a realistic composite aircraft fuselage is experimentally studied. The control inputs are due to piezoelectric actuators bonded to the cylinder wall while error information from the interior acoustic field is sensed by microphones. A preliminary analytical development was conducted to investigate the mechanisms of the structural/acoustic coupling exhibited by a simple cylindrical model in order to gain more inSight into the coupling properties of the piezoelectric actuators with the cylinder. Therefore, the response of a homogeneous, simply-supported cylindrical shell to the excitation of piezoelectric actuators was presented. The analytical results show that a piezoelectric actuator pair excited in-phase (stretching model) created a lower order circumferential interior acoustic field, more suitable to control the interior noise at low frequency than the same piezoelectric actuator pair excited in out-of-phase (bending model). The experiments were performed in the large anechoic chamber of the Acoustics Research Laboratory at NASA Langley Research Center at Hampton, Virginia and utilized a 1.68 m diameter, 3.66 m length composite aircraft structure, equipped with stringers, ring frames and a cabin floor. The narrowband controller used in these experiments was a four channel adaptive LMS algorithm implemented on a TMS320C25 system board. Results showed that global reduc1:ion of the interior sound pressure level of the order of 12 dB could be obtained using piezoelectric actuators. The influence of the sensor/actuator location and configuration as well as the frequency of excitation was studied. In general this investigation validates active control using piezoelectric actuators bonded to the fuselage to reduce the interior noise inside realistic aircraft structures. / Master of Science