![]() ![]() Acoustic metamaterials for sound focusing and confinement. Extraordinary acoustic transmission through a 1D grating with very narrow apertures. Extraordinary sound screening in perforated plates. Acoustic cloaking in two dimensions: A feasible approach. A homogenization route towards square cylindrical acoustic cloaks. Scattering theory derivation of a 3D acoustic cloaking shell. Acoustic cloaking in three dimensions using acoustic metamaterials. On cloaking for elasticity and physical equations with a transformation invariant form. Full-wave invisibility of active devices at all frequencies. Overcoming the diffraction limit in wave physics using a time-reversal mirror and a novel acoustic sink. Confining and slowing airborne sound with a corrugated metawire. Collimation of sound assisted by acoustic surface waves. Ultrasonic metamaterials with negative modulus. The fabricated acoustic hyperlens relies on straightforward cutoff-free propagation and achieves deep-subwavelength resolution with low loss over a broad frequency bandwidth. Here, we report the experimental demonstration of an acoustic hyperlens that magnifies subwavelength objects by gradually converting evanescent components into propagating waves. However, these proposed approaches suffer narrow working frequency bands and significant resonance-induced loss, which hinders them from successful experimental realization. These could markedly enhance the capabilities in underwater sonar sensing, medical ultrasound imaging and non-destructive materials testing. Recent theories suggested that imaging below the diffraction limit using passive elements can be realized by acoustic superlenses or magnifying hyperlenses 15, 16. Acoustic metamaterials can manipulate sound waves in surprising ways, which include collimation, focusing, cloaking, sonic screening and extraordinary transmission 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14. ![]()
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