WAVES AND VIBRATIONS IN INHOMOGENEOUS STRUCTURES ...

ARTICLE IN PRESS
J.S. Jensen / Journal of Sound and Vibration 266 (2003) 1053–1078 1075
Fig. 15. The response in points A and B with a path of defects in the periodic structure for a the structure, (a) for
vertical path, and (b) for a corner path. The insets show schematics of the paths. Type 1 unit cells with Mx ¼ My ¼ 21:
whereas in point A the response remains high indicating that the signal is now confined to the
path. Fig. 15b shows the response for the bent path leading to point B. The response is now seen
to be normalized in B inside the band gap, whereas in point A the response drops.
Contour plots of the response for the two lattice structures with paths are shown in Figs. 16a
and b, respectively. The frequency of excitation for both figures is O ¼ 52:1 kHz; i.e., inside the
band gap. The figure shows how the paths of defects in the periodic structures effectively isolates
the vibrations to the path regions and thus ‘‘leads’’ the vibrations to the structural point A or B,
whereas away from the paths the response drops rapidly with distance.