MIT News November 20, 2024 Challenges in miniaturizing and characterizing acoustic metamaterials in high-frequency (megahertz) regimes have hindered progress toward experimentally implementing ultrasonic-wave control. A team of researchers in the US (MIT, Kansas City National Security Campus) presented an inertia design framework based on positioning microspheres to tune responses of 3D microscale metamaterials. They demonstrated tunable quasi-static stiffness by up to 75% and dynamic longitudinal-wave velocities by up to 25% while maintaining identical material density. The researchers explored the tunable static and elastodynamic property relation. According to the researchers their design framework expands the quasi-static and dynamic metamaterial property space […]
Category Archives: Sound
Researchers make sound waves travel in one direction only, with implications for electromagnetic wave technology
Phys.org September 6, 2024 Breaking the reciprocity of wave propagation is a problem of fundamental interest, and a much-sought functionality in practical applications, both in photonics and phononics. Although it has been achieved using resonant linear scattering from cavities with broken time-reversal symmetry, such realizations have remained inescapably plagued by inherent passivity constraints, which make absorption losses unavoidable, leading to stringent limitations in transmitted power. Researchers in Switzerland solved this problem by converting the cavity resonance into a limit cycle, exploiting the uncharted interplay between non-linearity, gain, and non-reciprocity. Strong enough incident waves could synchronize with these self-sustained oscillations and […]
Researchers move floating objects with soundwaves
Phys.org July 25, 2024 Light and sound waves can move objects through the transfer of linear or angular momentum. However, the stringent requirement for a highly controlled, low-reverberant and static environment still hinders the applicability of these techniques in many scenarios. An international team of researchers (Kazakhstan, Switzerland, France, Austria) overcame this challenge and demonstrated the manipulation of objects in disordered and dynamic media by optimally tailoring the momentum of sound waves iteratively in the far field. The method did not require information about the object’s physical properties or the spatial structure of the surrounding medium but relied only on […]
Metalens expands Its reach from light to sound
Science Daily May 14, 2024 An important hurdle for using metalenses for manipulating waves is due to the severe hampering of the angular response originating from coma and field curvature aberrations, which result in a loss of focusing ability. Researchers in South Korea developed a blueprint by introducing the notion of a wide field-of-hearing (FOH) metalens, designed particularly for capturing and focusing sound with decreased aberrations. Employing an aberration-free planar-thin metalens that leverages perfect acoustic symmetry conversion, they experimentally realized a robust wide FOH capability of approximately 140 deg. in angular range. The metalens featured a relatively short focal length, […]