Figure 4
From: Hierarchical phononic crystals for filtering multiple target frequencies of ultrasound
Effects of total filling fraction (γtot) on phononic bandgaps. Bandgaps of HPCs for different total filling fractions of Al for (a) N = 0, (b) N = 1 and (c) N = 2. The black and white areas indicate stopbands and passbands, respectively. For each structure, the filling fractions of the embedded structures are identical, which means \({\gamma }_{0}={\gamma }_{1}={\gamma }_{tot}^{1/2}\) in the case of N = 1. The other geometrical parameters are taken as \(\{{l}_{0}=1\,{\rm{c}}{\rm{m}},{n}_{0}=10\}\), \(\{{l}_{0}=1\,{\rm{c}}{\rm{m}},{n}_{0}=10,{n}_{1}=3\}\), and \(\{{l}_{0}=1\,{\rm{c}}{\rm{m}},{n}_{0}=10,{n}_{1}={n}_{2}=3\}\) for the respective structures.
