By analogy with the electromagnetic wave, the acoustic transparency phenomenon is analyzed for a multilayered sphere with acoustic metamaterials. The neutral-inclusion concept is used to predict the transparency conditions in the quasistatic case, which are further confirmed by a full-wave analysis. The mechanism of the transparency is based on lowering the total-scattering cross section of the...

Obtrusions such as bends, constrictions and junctions occurring in confined flows give rise to turbulent flow structures and separation zones. The acoustic analysis of the flow-induced noise may be accomplished using two different approaches. The first is the highest modeling approach, wherein the full set of compressible Navier Stokes equations is solved. Difficulties lie in the amplitude disp...

Absorbing sound almost completely at specific frequencies with conventional acoustic materials whose thickness is least 60 times smaller than the wavelength a challenge, particularly low frequencies. Fort this purpose, metamaterials are of great interest. Here, metamaterial called multi-pancake cavities. It composed main pore repetition thin annular cavities (pancake cavities). Previous researc...

The drag and noise reduction of the flow around a cylinder is one important topics in hydrodynamics acoustics. In this paper, three typical bionic cylinders are designed based on serrated structure surface shark skin. Using Large eddy turbulence model Lighthill’s acoustic analogy method, characteristics smooth kinds at different Reynolds numbers were compared, was optimized. results show that m...

Acoustic holographic rendering in complete analogy with optical holography are useful for various applications, ranging from multi-focal lensing, multiplexed sensing and synthesizing three-dimensional complex sound fields. Conventional approaches rely on a large number of active transducers and phase shifting circuits. In this paper we show that by using passive metamaterials as subwavelength p...

Unruh [1] demonstrated that black holes have an analogy in acoustics. Under this analogy the acoustic event horizon is defined by the set of points in which the local background flow exceeds the local sound speed. In past work [2], we demonstrated that under a white noise source, the acoustic event horizon will radiate at a thermal spectrum via a classical tunneling process. In this work, I sum...

A balloon filled with a gas that has a different sound speed than that of air has been used by science teachers in the past as an ”acoustic lens.” One purpose of the lens is to show refraction of sound waves as an analogy to geometric optics [H. Kruglak and C. C. Kruse, Am. J. Phys. 8, 260-261 (1940)]. This paper discusses the physics involved with the balloon lens demonstration. In order to de...