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Description
Coupled elastoacoustic problems, involving the interaction between an acoustic field and a vibrating structure, play a central role in low- and mid-frequency vibroacoustics. Displacement-based formulations are attractive due to their symmetry and their natural description of structural dynamics; however, their extension to the acoustic field often leads to numerical difficulties, such as spurious rotational modes and challenges in enforcing interface continuity. In this work, we present a displacement-based formulation that preserves the irrotational nature of the acoustic field by construction. The approach is developed within a Rayleigh–Ritz framework, using acoustic particle displacement and structural displacement as primary variables, and employs spatial derivatives of Gaussian basis functions to obtain symmetric algebraic systems while avoiding spurious circulation modes.A key feature of the method is the treatment of the fluid–structure interface. Displacement continuity is enforced strongly via a nullspace method, eliminating the need for explicit coupling matrices, while traction continuity is naturally satisfied in a weak sense through the variational formulation. This results in a monolithic and numerically robust solution strategy for coupled interaction. The approach is validated through a set of benchmark problems of increasing complexity showing excellent agreement with finite element solutions in terms of modal frequencies and mode shapes.