A transformation of the CVIS method to eliminate the irregular frequency

The simple-source method implies an interior virtual fluid field for the exterior acoustic radiation problems. Due to the resonance of this virtual fluid field, the emergence of the irregular frequencies (fictitious frequency) will occur on certain frequencies, which lead to the distortion of the results. It is a purely mathematical problem that the boundary integral equation has no solution at irregular frequencies. Based on the closed virtual impedance surface method (CVIS method), a constant transformation factor α is introduced to form a transformation of the CVIS method, the CVIS-α method. Through the method, the irregular frequencies can be effectively eliminated. Meanwhile, the partial derivatives of the Green's function can be ignored in the boundary integral equation, which is for the exterior acoustic problems. This method has natural advantages in the integrated calculation of acoustic radiation and propagation of 3D elastic floating body in the ocean acoustic environment. The validity of the method is verified by the acoustic impedance calculation cases of the spherical and cylindrical floating bodies. Moreover, some optimization principles for building the CVIS are given in consideration of both the computing quantity and the eliminating effect.