Experimental study of active sound transmission control into enclosed spaces

The transmission of sound into enclosures, such as an aircraft cabin, generally occurs through thin-walled panels. In order to actively reduce the sound radiation of vibrating structures, far-field sound power is often the quantity to be suppressed. In reality, the interior sound field interacts with the structural vibration and an exchange of energy occurs. To account for the interaction, the enclosure dynamics need to be included into the controller formulation.This study examines different active vibration control (AVC) and active structural-acoustic control (ASAC) concepts by experimental means. A rectangular aluminum plate in contact to an acoustic enclosure is used for a comparative evaluation of control performance. Structural sensors and actuators are used, for the purpose of suppressing the acoustic response inside the enclosure. For studies regarding ASAC, additional radiation filters of interior sound radiation are designed in order to incorporate the enclosure dynamics in the control path. A reduction of sound radiation is estimated by microphone measurements inside the enclosure and compared for the different control concepts.