An homogeneous piezoelectric rod is shown to exhibit Bragg band gaps when an electrical boundary condition is applied periodically with the help of metallic electrodes. An analytical model is developed which formulation depends on the applied electric boundary condition and reveals that Bragg band gaps occurring in this very peculiar phononic crystal are related to the electric charge located on the electrodes. Moreover, via an accurate boundary condition (electrodes connected in short circuit, in open circuit, or through an external capacitance), full tunability of the Bragg band gaps can be achieved. Measurements of ultrasonic transmission present an overall excellent agreement with the theoretical results. This phononic crystal can be easily manufactured and presents many potential applications as frequency filters especially for radio frequency telecommunications. V

This paper reports on numerical and experimental results of acoustic transmission spectra of bead chains with symmetric and asymmetric Fibonacci-like structures. As a matter of comparison, perfect periodic acoustic waveguide structures are also examined. This study shows that Fibonacci structures with mirror symmetry can exhibit localized modes with higher amplitude, due to resonant transmission induced by the presence of dimers inside the 1D structure. A good agreement is observed between the theoretical predictions and the experimental power spectra. V

A one-dimensional stack of identical piezoelectric rods is investigated. The device exhibits a band gap related to electrical boundary condition. A separate control of the central frequency and of the width of the band gap is performed by an electrical boundary condition involving two different variable capacitances. Because the capacitances are grounded, a specific model has been developed and validated. Finally, experiments unambiguously confirmed previous theoretical observations.