Abstract
In this work, numerical methods to identify the surface areas of a vibrating structure that radiate sound are implemented for cases of structures with inhomogeneous distributions of viscous Rayleigh damping. The intensity-based techniques correspond to acoustic intensity evaluated in terms of the acoustic pressure and particle velocity, non-negative intensity evaluated in terms of the acoustic impedance matrix obtained at the structural surface, and back-calculated non-negative intensity evaluated in terms of the acoustic impedance matrix obtained at a far-field receiver surface. Different configurations of inhomogeneous damping are applied to two elastic structures corresponding to a plate and a cylindrical shell. To examine the influence of inhomogeneous damping on sound radiation, the acoustic intensity on the structural surface, the acoustic intensity on several different far-field receiver surfaces, non-negative intensity and back-calculated non-negative intensity are numerically compared for different inhomogeneous damping cases.
Highlights
To reduce exterior structure-borne sound, identification of the contribution to radiated sound from individual components of a vibrating structure is important
Inspection of the real and imaginary parts of the particle velocity revealed traveling waves propagating to regions with higher damping
Regions with higher damping dissipate bending waves act as energy sinks, which in turn was shown to contribute more energy to the far-field acoustic intensity
Summary
To reduce exterior structure-borne sound, identification of the contribution to radiated sound from individual components of a vibrating structure is important. The surface contribution method was renamed as non-negative intensity (NNI) by Williams.[10] Results obtained using both NNI and SSI to identify the surface areas of arbitrarily-shaped vibrating structures that radiated sound have been recently compared using both a sound power ratio and the modal assurance criterion.[11] Supersonic intensity was found to be difficult to implement at low frequencies due to the size of the spatial radiation filter. Back-calculated NNI evaluated on different far-field surfaces that do not fully circumscribe the structure was found to generate markedly different results, highlighting the ability of back-calculated NNI to identify regions on a rigid or elastic structure that contribute to directional structure-borne sound. Results obtained using NNI evaluated on the surface of the structure and back-calculated NNI on the far-field receiver surfaces for the homogeneous and inhomogeneous damping cases are compared to those for acoustic intensity. For the low frequencies considered in this work, NNI and back-calculated NNI show markedly different results to those obtained using acoustic intensity
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