Conclusions We have demonstrated theoretically by using the TMM and experimentally by acoustic transmission measured directly, the formation of acoustic cavity

modes in GHz frequencies by introduction of defects into periodic structures based on PS. Acoustic resonances can be tuned at different frequencies by changing the porosity of the defect. And we proved that these resonant modes appear due to the localization of the field into the defect. The acoustic mirrors and cavity structures based on PS have a performance which is at least comparable with that devices based on semiconductor superlattices. This study could be useful for the design of acoustic devices, such as highly selective frequency filters with applications in GHz range. Acknowledgements The authors acknowledge CONACyT for support under CB-839 solubility dmso project No. 167939. References 1. Kushwaha MS, Halevi P, Dobrzynski L, Djafari-Rouhani B: Acoustic band structure of periodic elastic composites. Phys Rev Lett 1993, 71:2022. 10.1103/PhysRevLett.71.2022CrossRef 2. Kushwaha MS, Halevi P, Martínez G: Theory of acoustic band structure of periodic Screening Library datasheet elastic composites. Phys Rev B 1994, 49:2313. 10.1103/PhysRevB.49.2313CrossRef 3. Sigalas MM, Economou EN: Attenuation of multiple-scattered sound. Europhys Lett 1996, 36:241. 10.1209/epl/i1996-00216-4CrossRef 4. Kushwaha

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