  When waves are propagated through a medium with scatters and these elements
are positioned periodically, as in the crystal structures, multiple scattering
leads to a phenomenon known as banded structures. This means that waves can
propagate in a certain frequency range, according to rules of dispersion, while
in other frequency ranges the propagation is cancelled. The first are called
allowed bands and the last deaf bands. This work part in order to verify the
existence of forbidden bands in the zone of ultrasonic frequency to triangular
structures formed by cylinders (hollow and solid) of different diameters (8 and
16mm.). The results indicate that the triangular structure has selective
attenuation zones, obtaining results similar to those theoretically predicted
for the two main directions of symmetry (0 and 30).
