Substructuring methods are a very common and efficient way to solve complex vibroacoustic problems. The Condensed Transfer Function (CTF) approach is a substructuring method based on the concept of subsystem condensed transfer functions (corresponding to admittances or impedances) that allows assembling acoustical or mechanical subsystems coupled along lines or surfaces. For certain practical applications, it may be more efficient to subtract or to decouple a subsystem to a global system rather than assembling different subsystems. In this paper, a reverse formulation of the CTF method is proposed. This formulation allows us to predict the behavior of a subsystem that is part of a larger system, from the knowledge of the condensed transfer functions (CTFs) of the global system and of the residual subsystem that must be removed. For purposes of validation, the scattering problem of a rigid sphere in an infinite water domain impacted by an acoustic plane wave is considered. Comparisons with theoretical calculations are used to validate the formulation proposed and permit studying its accuracy for two types of condensation functions defining the CTFs.

Decoupling procedures based on substructuring methods allow to predict the vibroacoustic behaviour of a given system by removing a part of an original system that can be easily modelled. The reverse Condensed Transfer Function (rCTF) method has been developed to decouple acoustical or mechanical subsystems that are coupled along lines or surfaces. From the so-called condensed transfer functions (CTFs) of the original system and of the removing part, the behaviour of the system of interest can be predicted. The theoretical framework as well as a numerical validation have been recently published. In the present paper, we focus on the influence of numerical errors on the results of the rCTF method, when the CTFs are calculated using numerical models for the original system and/or the removed part. The rCTF method is applied to a test case consisting in the scattering problem of a rigid sphere in an infinite water domain and impacted by an acoustic plane wave. Discrete green formulation and finite element method are used to estimate the CTFs. Numerical results will be presented in order to evaluate the sensitivity of the method to model errors and the potential promises and limitations of the method will be highlighted.

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