1.8 Reflection of sound waves at acoustically hard surfaces................. Competition Wizard Magazine Pdf. 1.8.1 Specular reflection. Sound waves can propagate in air, in liquids or in solid bodies. Figure 1.1 shows plane wave. Theoretical acoustics analytical and numerical methods for sound field calculations. Nonlinear acoustics nonlinear. Australian Army Combat Survival Manual. In this paper we demonstrate by means of numerical simulations the phenomenon of extraordinary transmission of surface acoustic waves in solids. The colour scale refers to the simulated surface wave normal particle velocity corresponding to the wave field calculated 0.4 ns after excitation.

Extraordinary transmission of waves, i.e. A transmission superior to the amount predicted by geometrical considerations of the aperture alone, has to date only been studied in the bulk. Here we present a new class of extraordinary transmission for waves confined in two dimensions to a flat surface. By means of acoustic numerical simulations in the gigahertz range, corresponding to acoustic wavelengths λ ~ 3–50 μm, we track the transmission of plane surface acoustic wave fronts between two silicon blocks joined by a deeply subwavelength bridge of variable length with or without an attached cavity. Several resonant modes of the structure, both one- and two-dimensional in nature, lead to extraordinary acoustic transmission, in this case with transmission efficiencies, i.e.

Intensity enhancements, up to ~23 and ~8 in the two respective cases. We show how the cavity shape and bridge size influence the extraordinary transmission efficiency. Applications include new metamaterials and subwavelength imaging.

Espacio De Almacenamiento Insuficiente Para Procesar Este Comando Windows Installer. The subject of extraordinary optical transmission through an array of subwavelength holes arose from measurements in the far infra-red and visible wavelength ranges in metal apertures. This work inspired extensive studies on the analogous extraordinary acoustic transmission phenomenon. This was theoretically predicted for bulk waves,,,,,, and experimentally verified in a wide variety of grating, slit and hole systems,,,,,,. Several types of transmission mechanism were proposed for acoustic extraordinary transmission, in particular periodic-lattice resonances, Fabry-Perot-type resonances, elastic Lamb-mode-resonances, Helmholtz resonators, membrane resonances and space coiling.

Experiments on the passage of Rayleigh waves through a fluid channel have demonstrated anomalously low acoustic transmission at certain frequencies. However, in spite of the interesting possibilities in the fields of metamaterials and subwavelength imaging, the extraordinary transmission of surface waves, and in particular surface acoustic waves, has never been investigated. This is surprising in view of the potential simplifications introduced by reducing the dimensionality of the extraordinary transmission problem to waves confined to a plane, with potential applications in miniaturization of the overall geometry. In this paper we demonstrate by means of numerical simulations the phenomenon of extraordinary transmission of surface acoustic waves in solids. We first consider the case of a straight waveguide in the form of a deeply subwavelength-width bridge joining two blocks. We also consider a bridge structure containing a resonant cavity. With these structures we demonstrate transmission efficiencies up to ~23, calculated from the intensity enhancement over a region sampling the transmitted surface acoustic field.

For both types of structure we choose microscopic sizes in order to give acoustic resonances in the gigahertz range, as such frequencies correspond to those used in surface acoustic wave filters and devices. Furthermore, direct surface acoustic wave imaging techniques exist for this frequency range,,,, and so our work is therefore experimentally realizable. The sample consists of a crystalline Si (100) substrate divided into three regions— two blocks and a connecting bridge— as shown in. Silicon was chosen because of the relative ease of future sample preparation. The left-hand (right-hand) block is of dimensions 150 × 110 μm 2 (55 × 110 μm 2) as seen from the top. The bridge connecting the two blocks is of lateral thickness W = 0.25 μm and variable length L (as shown in inset (a)), the former dimension chosen to be much smaller than the acoustic wavelength λ (~5 μm at 1 GHz, so W ~ λ/20 at this frequency).