In this study, we show that robust and tunable acoustic asymmetric transmission can be achieved through gradient-index metasurfaces by harnessing judiciously tailored losses. We theoretically prove the wave behavior stems from loss-induced suppression of high order diffraction. further experimentally demonstrate novel phenomenon. Our findings could provide new routes to broaden applications for lossy metamaterials metasurfaces.

We report the experimental demonstration of broadband negative refractive index obtained in a labyrinthine acoustic metamaterial structure. Two different approaches were employed to prove nature: one-dimensional extractions effective parameters from reflection and transmission measurements, two-dimensional prism-based measurements that convincingly show angle corresponding refraction. The angles observed latter case also agree very well with numerical simulations. expect this become unit...

An impedance matched surface is able, in principle, to totally absorb the incident sound and yield no reflection, this desired many acoustic applications. Here we demonstrate a design of absorbing with simple construction. By coupling different resonators generating hybrid resonance mode, designed fabricated metasurface that impedance-matched airborne at tunable frequencies subwavelength scale unit cells. With careful coupled resonators, over 99% energy absorption central frequency 511 Hz...

Acoustic tweezers have recently raised great interest across many fields including biology, chemistry, engineering, and medicine, as they can perform contactless, label-free, biocompatible, precise manipulation of particles cells. Here, we present wave number-spiral acoustic tweezers, which are capable dynamically reshaping surface (SAW) wavefields to various pressure distributions facilitate dynamic programmable particle/cell manipulation. SAWs propagating in multiple directions be...

We present five kinds of labyrinthine or space-coiling acoustic metamaterials with tapered channels and apertures. These designs exhibit negative index behavior modest dispersion, also have substantially improved impedance matching compared to previously investigated cells. Experimentally measured effective material parameters are in good agreement numerically computed results for the first two designs. Numerical presented other three unit By virtue their design tunability small size, these...

In this Letter, we report on the design and experimental characterization of a broadband acoustic hyperbolic metamaterial. The proposed metamaterial consists multiple arrays clamped thin plates facing y direction is shown to yield opposite signs effective density in x directions below certain cutoff frequency, therefore, yielding dispersion. Partial focusing subwavelength imaging are experimentally demonstrated at frequencies between 1.0 2.5 kHz. could open up new possibilities for wave...

We present a design of acoustic metasurfaces yielding asymmetric transmission within certain frequency band. The consists layer gradient-index metasurface and low refractive index metasurface. Incident waves are controlled in wave vector dependent manner to create strong transmission. Numerical simulations show that the approach provides high contrast between two incident directions designed This is further verified by experiments. Compared previous designs, proposed yields compact planar...

Abstract 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 phase shifting circuits. In this paper we show that by using passive metamaterials as subwavelength pixels, can be achieved without cumbersome circuitry only single transducer, thus significantly...

We present here two diffractive acoustic lenses with subwavelength thickness, planar profile, and broad operation bandwidth. Tapered labyrinthine unit cells their inherently broadband effective material properties are exploited in our design. Both the measured simulated results showcased to demonstrate lensing effect over more than 40% of central frequency. The focusing a propagating Gaussian modulated sinusoidal pulse is also demonstrated. This work paves way for designing generalized phase...

Conventional sound shielding structures typically prevent fluid transport between the exterior and interior. A design of a two-dimensional acoustic metacage with subwavelength thickness which can shield waves from all directions while allowing steady flow is presented in this paper. The structure designed based on gradient-index metasurfaces composed open channels shunted Helmholtz resonators. In-plane at an arbitrary angle incidence reflected due to strong parallel momentum surface, leads...

Designing a "cocktail party listener" that functionally mimics the selective perception of human auditory system has been pursued over past decades. By exploiting acoustic metamaterials and compressive sensing, we present here single-sensor listening device separates simultaneous overlapping sounds from different sources. The with compact array resonant is demonstrated to distinguish three independent sources 96.67% correct audio recognition. Segregation signals achieved using physical layer...

Acoustic metasurfaces provide useful wavefront shaping capabilities, such as beam steering, acoustic focusing, and asymmetric transmission, in a compact structure. Most described the literature are transmissive devices focus their performance on steering sound of fundamental diffractive order. In addition, range incident angles studied is usually below critical incidence predicted by generalized Snell's law reflection. this work, we comprehensively analyze wave interaction with generic...

Abstract The Luneburg lens is a spherically symmetrical gradient refractive index (GRIN) device with unique imaging properties. Its wide field-of-view (FoV) and minimal aberration have lead it to be successfully applied in microwave antennas. However, only limited realizations been demonstrated acoustics. Previously proposed acoustic lenses are mostly inherently two-dimensional designs at frequencies from 1 kHz 7 kHz. In this paper, we apply new design method for scalable self-supporting...

Realization of non-reciprocal devices, such as isolators and circulators, is fundamental importance in microwave photonic communication systems. This can be achieved by breaking time-reversal symmetry the system or exploiting nonlinearity topological effects. However, exploration devices remains scarce acoustic In this work, sound propagation a space-time modulated medium theoretically studied. Finite-difference time-domain (FDTD) simulations are carried out to verify results....

This work reports a method for fabricating three-dimensional microwave metamaterials by fused deposition modeling 3D printing of highly conductive polymer composite filament. The conductivity such filament is shown to be nearly equivalent that perfect conductor metamaterial applications. expanded degrees-of-freedom made available designs are demonstrated designing, fabricating, and testing 3D-printed unit cell with broadband permittivity as high 14.4. measured simulated S-parameters agree...

Abstract We report on the development of an easily deployable LF near‐field interferometric‐time arrival (TOA) 3‐D Lightning Mapping Array applied to imaging entire lightning flashes. An interferometric cross‐correlation technique is in our system compute windowed two‐sensor time differences with submicrosecond resolution before TOA used for source location. Compared previously reported location systems, captures many more sources. This due mainly improved mapping continuous processes by...

A design approach for acoustic metamaterial unit cells based on a coiled path with impedance matching layers (IMLs) is proposed in this paper. theoretical developed to calculate the transmission of labyrinthine different effective refractive indices. The IML introduced broaden bandwidth and produce lower envelope boundary According theory, all indices can be built achieve unitary at center working frequencies. frequency tuned by adjusting length IML. Numerical simulations finite element...

Systems that break transport reciprocity have recently opened exciting possibilities for wave manipulation. Here we report nonreciprocal acoustic transmission in cascaded resonators are modulated space and time. An analytic approach is developed the design strategy discussed realizing a physical system based on this approach. The theory verified numerically by finite-difference time-domain (FDTD) simulations, with one-way isolation factor greater than 25 dB out of just two resonators. Our...

Over the past few years, acoustic gradient index metasurfaces (GIMs) have been actively studied for numerous wave control capabilities that they facilitate. Previous research, however, has primarily focused on GIMs operate in audible frequency range, due to difficulties fabricating such intricate structures at millimeter and submillimeter scales, ultrasonic applications. In this work, we design, fabricate, experimentally demonstrate working of a hybrid resonant metasurface airborne...

We propose and demonstrate a compact acoustic retroreflector that reroutes probing signals back towards the source with minimal scattering. Gradient refractive index (GRIN) metamaterials, based on Archimedean spiral structures, are designed to fulfill required profile. The experiments show retroreflector, whose radius is only approximately one wavelength, works in an incident angular range up 120 degrees over relatively broad bandwidth of about 27% central frequency. Such retroreflectors can...

Optical conformal mapping has been used to construct several isotropic devices with novel functionalities. In particular, a cloak could confer omnidirectional invisibility. However, the maximum values of refractive indexes needed for current designs are too large implement, even in microwave experiments. Furthermore, most designed so far have had imperfect impedance matching and therefore incomplete invisibility Here we describe perfect invisible device full everywhere. The value index...

An impedance matched surface is able, in principle, to totally absorb the incident sound and yield no reaction, this desired many acoustic applications. Here, we demonstrate a new design of absorbing with simple construction. By coupling di�erent resonators generating hybrid resonance mode, designed fabricated metasurface that impedance-matched airborne at tunable frequencies subwavelength scale unit cells. With careful coupled resonators, over 99% energy absorption central frequency 511 Hz...