In this work, a phononic metamaterial that could be applied for both acoustic and elastic wave attenuation is numerically examined. The hollow yablonovite structure with the addition of hollow spheres on a face-centered cubic arrangement is examined numerically, and wide bandgaps are found for the propagation of acoustic and elastic waves. The calculations were performed by using the finite element method. The research includes an investigation of all the geometric parameters of the structure and how the bandgaps are being affected from the values of each parameter. The proposed structure is found to have wide bandgaps for both elastic and acoustic waves. These findings strongly indicate that the proposed acoustoelastic metamaterial is a powerful candidate for several applications such as sound and vibrations attenuation, noise reduction, and acoustic filtering.

The tunable bandgaps of three-dimensional phononic structures with hollow spheres and rods were numerically examined. The Yablonovite Structure with the addition of spheres in Face Center Cubic arrangement was examined first. In addition, three-dimensional structures that have Simple Cubic and Base Centered Cubic symmetries have been examined with similar tunability behavior as the Yablonovite Structure. The calculations were performed by using the Finite Difference Time Domain method. The effect in the tunability of the bandgaps from different materials of the structure or fluids penetrating the structure and the effect of the geometrical parameters of the structures were also examined. The results showed that tunable phononic bandgaps could be achieved depending on the properties of the fluid that penetrates the hollow part of the structure. The performance of the Yablonovite Structure with spheres when placing defects was the last part of this research. The results of this work indicate that the practical design of tunable acoustic devices such as waveguides, sensors, and filters can be made through changing the properties of the constitutive materials and via fluid–solid interaction.

Phononic crystals and acoustic metamaterials are expected to become an important enabling technology for science and industry. Currently, various experimental methods are used for evaluation of acoustic meta-structures, such as impedance tubes and anechoic chambers. Here we present a method for the precise characterization of acoustic meta-structures that utilizes rapid broadband acoustic pulses generated by point-like and effectively massless laser plasma sound sources. The method allows for broadband frequency response and directivity evaluations of meta-structures with arbitrary geometries in multiple sound propagation axes while also enabling acoustic excitation inside the structure. Experimental results are presented from acoustic evaluations of various phononic crystals with band gaps in the audible range, notably also in the very low frequencies, validating the predictions of numerical models with high accuracy. The proposed method is expected to boost research and commercial adoption of acoustic metamaterials in the near future.

In this work, a phononic metamaterial that could be a reliable solution for several sound attenuation applications is examined numerically and experimentally. The proposed structure consists of a spherical shell connected with cylindrical conduits in a simple cubic arrangement. Numerical calculations, using the finite element method, and experimental measurements of the sound transmission loss were performed, providing significant evidence of the applicability of the proposed metamaterial in sound attenuation applications. For the validation of the complete acoustic bandgaps by the structure, the research was expanded to the examination of all high symmetry spatial directions. The results for all the examined spatial directions provided wide acoustic bandgaps, thus validating the evidence of complete acoustic bandgaps by the structure over a wide frequency range of the audio spectrum. Furthermore, the contribution of each part of the structure was separately analyzed, providing the physical insight for a deeper understanding of the response of the structure and the principal mechanism of the bandgap formation. The findings of this research prove that the proposed metamaterial could be a functionable unit for efficient sound attenuation applications.

In this work, a phononic metamaterial suitable for several sound attenuation applications is numerically and experimentally examined. The proposed structure consists of a combination of spheres in a face-centered cubic arrangement with rods that form the Yablonovite Structure. The Sound Transmission Loss of the structure is experimentally examined. In addition, numerical calculations of the Sound Transmission Loss were performed by using the Finite Element Method. The research includes experimental and numerical validation of different geometric parameters of the structure. The Sound Transmission Loss of the proposed structure found to have wide values over a wide frequency range of the audio spectrum. The findings of this research strongly indicate that the proposed metamaterial is a powerful candidate for efficient sound attenuation applications.