The frequency response of a two-dimensional trusslike periodic panel is studied adopting the transfer matrix of a repeated cell. Intracell resonance occurs at relatively low frequencies, causing high modal density of the panel. Effects of panel curvature, sag of cell diagonal member, mass added by a liquid filling the cell cavity, and damping by constrained viscoelastic layers are studied parametrically.
Transmission of sound across a 2-D trusslike periodic panel in contact with an acoustic fluid on both its faces is analyzed. Elastic frequency response of the panel made of repeated cells is expressed using transfer matrices of the unit cell, and acoustic pressure of the fluid is expressed using a source boundary element method. Transmission loss (TL) of a panel is computed for two geometries and compared with measurements. These comparisons reveal differences that result from attenuation zones due to periodicity along one axis of the panel and response that is predominantly along the other axis. Conditions under which these differences disappear are explained. A nondimensional parameter, including the ratio of sound speeds in solid and fluid and the ratio of panel length to radius of gyration of the cross-section controls the drop in TL at coincidence, called strength of coincidence.
The effect of blockage on the acoustic propagation in finite cylindrical cavities is studied. The shift in acoustic resonances corresponding to longitudinal and transverse standing waves is determined from a simplified one-dimensional plane-wave theory and compared to a more precise threedimensional analysis based on a Green's function surface element method adopted to axisymmetric geometries. One-dimensional theory is qualitatively acceptable even for large blockage while details of the acoustic field are revealed only by the three-dimensional analysis.
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