Control of Sound Radiation and Reflection With Advanced Smart Foam Blankets

摘要

The control of low frequency sound into launch vehicle payload fairings remains an important AF problem. The past few years of the project have demonstrated the high potential of using smart foam blankets for efficiently reducing the interior sound levels in the payloads of launch vehicles in the low frequency region where standard blankets perform poorly. The approach investigated at VAL consists of a hybrid active-passive approach in which active tile elements are embedded into the conventional passive blanket treatment to improve its low frequency performance. The smart blanket or skin is designed to cover extended regions of the structure through which most of the acoustic power transmits. It functions by reducing the radiation impedance that the structure sees (effectively de-couples the structural motion from the acoustic field) without having to apply control forces directly to the structure itself. The smart skin approach is thus suitable for very stiff structures such as a typical payload fairing. The previous work of the project has demonstrated the potential of a single smart foam tile element. This presentation summarizes recent work focused on extending the system to multiple smart foam tiles applied to a fairing like structure.