Abstract;
In this paper, we prove theoretically and experimentally the existence of complete ultrasonic band gap in phononic crystal beam. The phononic beam structure studied is composed of a linear lattice array of square pillars on a beam, made with aluminum-fortal easily machinable at centimetric scale. Ultrasonic characterization of phononic beam guides shows the existence of a frequency range where the transmitted signals are strongly attenuated, due to the presence of ultrasonic band gap, in agreement with theoretical results predicted by finite element simulation. These structures present a potential for the use as energy loss reduction in micromechanical resonators at high frequency regime.