Slow sound propagation in a sonic crystal linear waveguide

Abstract

A linear waveguide along the [11] direction of a triangular sonic crystal, composed of aluminum cylinders in air is shown both experimentally and numerically to facilitate slow sound propagation. Supercell-based calculations through the finite element method reveal a band centered at approximately 16.0 kHz with 255 Hz span, exhibiting linear variation away from band edges, for the lattice constant and cylinder radii of 21.7 mm and 10.0 mm, respectively. The experimental setup is based on monitoring the propagation of a Gaussian-enveloped sinusoidal pulse at 16.0 kHz inside the waveguide. Numerical behavior of the Gaussian pulse is investigated by time-dependent finite-element computations. The experimental and numerical group velocities are found to be 26.7 m/s and 22.6 m/s, respectively. Being congruous with the experimental findings, numerical transient study of the system reveals significant longitudinal compression commensurate with the calculated group index.

The use of slow waves to design simple sound absorbing materials

“…This rapid change in transmission leads to strong dispersion giving rise to slow phase or group velocity waves whose frequency is centered on the narrow transmission band. 1 In acoustics, most of theoretical and experimental evidences of slow sound have been achieved by considering sound propagation in pipes with a series of detuned resonators (mostly Helmholtz resonators) separated by a subwavelength distance, 2 tuned or detuned resonators separated by half of the wavelength giving rise to a coupling between the resonators and the Bragg bandgap, 3 in a waveguided sonic crystals, 4 in lined ducts. 5 So far, only a few studies have been focusing on the dissipation (dispersion and attenuation) of slow sound propagation, even if it has been sometimes noticed or discussed.…”

Guidance of surface waves in a micron-scale phononic crystal line-defect waveguide

“…1 Phononic crystal cavities and waveguides, for instance, offer the possibility to tailor desirable dispersion properties, potentially leading to dramatically reduced group velocities. Acoustic wave guidance has been predicted 2-5 and shown to occur for bulk [6][7][8][9][10] or Lamb waves 11 in fluid/solid or solid/solid phononic crystals. At the micron-scale, phononic confinement of surface guided waves holds promises for applications in the radio-frequency (RF) regime.…”

Simultaneous Guidance of Surface Acoustic and Surface Optical Waves in Phoxonic Crystal Slabs

“…We do not further change the configuration of the PXC slab surface to improve the slow wave effects of these surface bands. As numerous attempts have been devoted to slow down light or sound in the PTC [43] or PNC [44,45] structures, it can be inferred that by finely tuning the geometrical parameters, the improvement of simultaneously slow sound and light can be realized in this kind of PXC structure. We believe the PXC surface waveguides can be adopted to study the optomechanical/acousto-optical interaction between the photonic and phononic guided modes [46][47][48].…”