Volume 133, Issue 4, April 2013
Index of content:
- STRUCTURAL ACOUSTICS AND VIBRATION 
Prediction of high-frequency vibration transmission across coupled, periodic ribbed plates by incorporating tunneling mechanisms133(2013); http://dx.doi.org/10.1121/1.4792361View Description Hide Description
Prediction of structure-borne sound transmission on built-up structures at audio frequencies is well-suited to Statistical Energy Analysis (SEA) although the inclusion of periodic ribbed plates presents challenges. This paper considers an approach using Advanced SEA (ASEA) that can incorporate tunneling mechanisms within a statistical approach. The coupled plates used for the investigation form an L-junction comprising a periodic ribbed plate with symmetric ribs and an isotropic homogeneous plate. Experimental SEA (ESEA) is carried out with input data from Finite Element Methods (FEM). This indicates that indirect coupling is significant at high frequencies where bays on the periodic ribbed plate can be treated as individual subsystems. SEA using coupling loss factors from wave theory leads to significant underestimates in the energy of the bays when the isotropic homogeneous plate is excited. This is due to the absence of tunneling mechanisms in the SEA model. In contrast, ASEA shows close agreement with FEM and laboratory measurements. The errors incurred with SEA rapidly increase as the bays become more distant from the source subsystem. ASEA provides significantly more accurate predictions by accounting for the spatial filtering that leads to non-diffuse vibration fields on these more distant bays.
Underwater sound scattering and absorption by a coated infinite plate with a distributed inhomogeneity133(2013); http://dx.doi.org/10.1121/1.4792353View Description Hide Description
This paper concerns itself with the scattering and absorption of underwater incident sound by a coated infinite plate with an attached distributed inhomogeneity. Its objective is to determine if the distributed inhomogeneity can provide additional local reflection, such that it only increases the signal-to-noise ratio for a hydrophone detector placed on the inhomogeneity without significantly decreasing the overall sound absorption of the coated plate.
133(2013); http://dx.doi.org/10.1121/1.4794369View Description Hide Description
An inverse acoustic scattering problem the main aim of which is to reconstruct the one-dimensional variation of the acoustical parameters of a spherical object is investigated. The problem is first formulated conventionally through a coupled system of integral equations, and then this system is reduced to one-dimensional form by using the orthogonality properties of spherical harmonics. The inverse problem is solved in an iterative fashion via classical Newton algorithm. Some numerical simulations are carried out to test the feasibility of the method as well as to see the effects of some parameters on the solution. It is shown that the method is very effective for the profiles having smooth variations provided that an appropriate initial guess is chosen. However, some of the classical disadvantages of the Newton type algorithms are also observed in numerical experiments which may limit the applicability of the method to a certain extent.