Description: One of the main attributes contributing to the competitiveness of rotorcraft, is the continuously increasing expectations for passenger comfort which is directly related with reduced vibration levels and reduced interior noise levels. Such expectations are amplified in the VIP market where people are used in the acoustic and vibration levels of civil and executive jets. One of the most critical excitations for interior noise in helicopters is the one from the gearbox. Thus, the structure-borne noise path (i.e. excitation propagating from mounting locations through the fuselage structure to the panels of the cabin and to the interior) must be captured in rotorcraft interior noise computations. This proposal addresses the need stated in the solicitation for developing physics based tools that can be used within a multi-disciplinary design-analysis-optimization for computing interior noise in rotorcraft applications. Currently, there is no robust simulation capability for this type of acoustic simulations. The hybrid FEA method can be used for structure-borne helicopter applications and can be integrated very easily (due to the finite element based model) with models from other disciplines within a multidisciplinary design environment. It combines conventional FEA with Energy Finite Element (EFEA) and it extends the frequency range of applicability of an existing finite element model by converting the elements that model the flexible panels into EFEA type of elements. A seamless Hybrid FEA capability of commercial quality will be developed based on MES' commercial EFEA code. UTRC will participate in the proposed effort for validating the new developments through comparisons to test data for a rotorcraft structure and for providing technical consultancy.