The control of wave propagation, which relies on the artificial media design, is an important topic in fundamental and applied research as well. Unusual acoustic properties have been observed in both phononic crystals, periodic structures allowing the control of the wave at the scale of the wavelength, and metamaterials in which the effect is expected at large wavelength compared to structuration size. Numerous functionalities have been demonstrated such as frequency filtering and demultiplexing, acoustic insulation, wave guiding, acoustic cloaking, negative refraction and super-resolution, pulse delaying and compression with different application fields such as telecommunication components, imaging and acoustic stealth. However, few phononic crystals and metamaterials have ended up as actual devices because of their lack of tunability: the control of wave propagation, often obtained for a limited frequency range, is completely defined by the geometry and physical properties of the constitutive materials at the fabrication stage. To bring to these devices tunability and re-configurability, which are nowadays essential to satisfy most professional system requirements, MIRAGES project aims at developing tunable and reconfigurable active phononic crystals and metamaterials which will include piezoelectric or magnetostrictive materials and will be controlled by electric or magnetic fields. Tuning of active materials elasticity will be insured by external electrical impedance variations for piezoelectric constituents or by DC magnetic bias for magnetostrictive materials. The establishment of generic models and technologies for the design, elaboration and optimization of active phononic crystals and metamaterials constitutes the first goal of the project. Theoretical and numerical models, elaboration processes and specific characterization set-ups will be developed to evaluate quantitatively the magnitude of properties variations provided by the different materials, structures and control methods and to identify the optimal solution in terms of tunability range, frequency and fabrication technology. In connection with this general concept, two goals related to specific applications are forecast in MIRAGES project: • the demonstration that the integration of a controllable active material within a phononic crystal bring a clear added value to an existing acoustic MEMS component used in telecommunications. Electric or magnetic control of one-dimensional magnetostrictive phononic crystal will be studied in the MHz range to realize either a switchable Bragg mirror, a post-fabrication finely tunable (less than 1%) Coupled Resonator Filter or a Fabry-Perot acoustic resonator with broad tuning (more than 10%). • the first realization of an electrically controlled gradient-index metamaterial or phononic crystal for stealth applications. To mimic sonar, the demonstrator will take the form of an active wall located between an acoustic source and a target. Constituted by a two-dimensional phononic crystal or metamaterial with piezoelectric inclusions, the wall will act as a countermeasure on the position, the speed and the orientation of a target. This demonstrator will fully exploit the possibilities given by the static, dynamic and real-time electric control of the artificial medium to shape the delay, the frequency content and the reflection angle of the reflected beam.