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    Broad omnidirectional acoustic band gaps in a three-dimensional phononic crystal composed of face-centered cubic Helmholtz resonator network
    (Acoustical Soc Amer Amer Inst Physics, 2021) Bicer, Ahmet; Korozlu, Nurettin; Kaya, Olgun A.; Cicek, Ahmet
    Broad omnidirectional band gaps in a three-dimensional phononic crystal consisting of a face-centered cubic array of spherical air voids connected by cylindrical conduits in solid background are numerically and experimentally demonstrated. With a low material filling fraction of 37.7%, the first bandgap covers 3.1-13.6 kHz frequency range with 126.1% gap-over-midgap ratio. Finite-element method is employed in band structure and numerical transmission analyses. Omnidirectional band gaps are observed in only two-period thick slabs in the 100, 110, and 111 orientations. Experimental transmission characteristics are in good agreement with numerical data. The phononic crystal can be employed in low-frequency sound proofing.& nbsp;(C) 2021 Acoustical Society of America
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    Ultrasonic Gas Sensing by Two-Dimensional Surface Phononic Crystal Ring Resonators
    (Amer Chemical Soc, 2019) Cicek, Ahmet; Trak, Digdem; Arslan, Yasin; Korozlu, Nurettin; Kaya, Olgun A.; Ulug, Bulent
    An acoustic ring resonator employing a two-dimensional surface phononic crystal is proposed for high-sensitivity detection in binary gas mixtures. Band analyses and frequency-domain simulations via the finite-element method reveal that a single band for spoof surface acoustic waves appears at ultrasonic frequencies around 58 kHz where modification of its dispersion due to varying gas composition results in a linear shift of the resonance frequency. The shift rate is -17.3 and 8.8 mHz/ppm for CO2 and CH4, respectively. The linear shift of resonance frequency is experimentally validated. In addition, the ring resonator can also be employed to track acoustic intensity variation with gas concentration, where exponentially decaying intensity for low concentrations leverages high-sensitivity operation.