Volume 134, Issue 6, December 2013
Index of content:
- STRUCTURAL ACOUSTICS AND VIBRATION 
134(2013); http://dx.doi.org/10.1121/1.4828822View Description Hide Description
Two elastic systems are considered in this work: A special linear chain of harmonic oscillators and a quasi one-dimensional vibrating rod. Starting in both cases with a locally periodic system formed by unit cells with a single element, these cells are converted into binary cells. The acoustic and optical bands then appear. For the vibrating rod experimental values are compared with theoretical results; in particular, the normal-mode amplitudes are obtained and the agreement is excellent.
Prediction of a body's structural impedance and scattering properties using correlation of random noise134(2013); http://dx.doi.org/10.1121/1.4828833View Description Hide Description
This paper derives a method to estimate the structural or surface impedance matrix (or equivalently the inverse of the structural Green's function) for an elastic body by placing it in an encompassing and spatially random noise field and cross-correlating pressure and normal velocity measurements taken on its surface. A numerical experiment is presented that utilizes a cross-correlation method to determine the structural impedance matrix for an infinite cylindrical shell excited by a spatially random noise field. It is shown that the correlation method produces the exact analytic form of the structural impedance matrix. Furthermore, using standard impedance formulations of the scattered and incident pressure fields at the object surface that are based on the equivalent source method and using this estimated structural impedance, a prediction of the scattered acoustic field at any position outside of the object can be made for any given incident field. An example is presented for a point (line) source near a cylindrical shell and when compared with the analytical result, excellent agreement is found between the scattered fields at a radius close to the shell.