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Global acoustic sensitivity analysis [1] is a technique used to identify structural modifications to a component that can reduce the total radiated power of a vibrating structure or the sound pressure levels at specified field points. This report describes the use of global sensitivity analysis within SYSNOISE to determine what structural changes are required to reduce radiated noise from flexible structures in an open duct system. The technique can help optimize design parameters that define the behavior of a flexible structure such as shell thickness and Young's Modulus. The sensitivity analysis approach consists of separately evaluating structural and acoustic sensitivities. A structural finite element model (FEM) of an open duct system is used to compute the sensitivity of the structural response to changes in thickness. A boundary element model (BEM) is then used to relate changes in the calculated acoustic response to changes in the structural design variables.