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The objective of this paper is to present the complex analysis method for the free vibration of general anisotropic rotors. The approach developed in this work represents the natural mode of the rotor as the sum of two sub-modes, one that rotates in the forward direction and the other in the backward direction. It is shown that the natural mode has to be described as such to satisfy the complex equation of motion of general rotor systems. Physical interpretation of results from the analysis of a model of the anti-symmetric motion of the rigid rotor shows that the complex mode contains modal directivity information as well as the conventional modal information. Proposed representation of the natural mode enables one to make clear definition of the forward mode and the backward mode, and more importantly enables one to complete the complex rotor analysis procedure.

In highly reverberant enclosures, the identification of noise sources is a difficult and time consuming task. One effective approach is the Inverse Frequency Response Function (IFRF) method. This technique uses the inverse of an acoustic FRF matrix, that when multiplied by operating pressure response data reveals the noise source locations. Under highly reverberant conditions the deployment of a sound absorbing body is especially useful in reducing the effects of resonant modes that obscure important information in the FRFs. Without the absorption, the IFRF method becomes practically difficult to perform in these environments due to poor conditioning of the FRF matrix. This study investigates the feasibility of using Boundary Element and Finite Element Methods to establish the frequency response functions between selected panel points and microphones in the array.