There are two waves propagating in the backing medium - a fast compressional wave and a slower transverse wave. The transverse wave gives rise to constructive interference at approximately +/- 40 degrees. This is shown by the straight line wavefronts propagating at +/- 40 degrees. With the exception of this artifact, this is a good array element with an omnidirectional, expanding wavefront. Finite Element Analysis is particularly useful for quantifying the quality of vibrational 'purity'. Problems in vibrational characteristics frequently map into imaging artifacts.
As the element vibrates it alternately extends and contracts with
the perpendicular dimensions vibrating anti-phase so that the element maintains
constant volume.
