Passive acoustic wave manipulations are severely constrained by the narrow frequency bandwidth of acoustic metastructures. In this research, an unprecedented type of reconfigurable acoustic metascreen is proposed for broadband manipulations of transmitted acoustic waves. The conceived structure is composed of uniquely designed unit cells producing the modulation of the transmitted phase shift within the full 2π range with an excellent impedance matching with the background medium. By rationally arranging the reconfigurable elements within the metascreen based on the corresponding parameter profile, different phenomena and functionalities can be easily realized. As examples, acoustic focusing and acoustic bending are presented to showcase the performance of the proposed metascreen. We indeed numerically and experimentally demonstrate the ultra‐broadband and reconfigurable features of our concept over an astonishing frequency range extending from 3 to 17 kHz, which covers the majority spectrum of the audible range of human hearing. Our work provides a unique and remarkable conceptual design of acoustic metascreen opening a promising and pragmatic route to conceive compact broadband acoustic devices, where wavefront manipulations on broadband sound signals or pulsed signals are required.

In this research, we propose and design an acoustic metamuffler (AMM) by coupling a micro-perforated plate and a composite waveguide formed by a main waveguide and a Helmholtz resonator. The proposed mechanism and the deliberately designed structure are conducive to generating multimode resonances which help to improve the coupling absorption effect and lead to a broadband (4 octaves) sound insulation. We develop an effective circuit model to analytically predict the insulation bandwidth and put forward numerical and experimental measurements that demonstrate the effectiveness of the proposed concept. The designed AMM produces sound insulation with an average of 20 dB of sound transmission loss at a low frequency range extending from 100 to 1600 Hz while having an ultrathin thickness of 6.2 cm (1/55λ for the lowest working frequency). Our findings could have pragmatic applications for acoustic insulators or absorbers.

We numerically and experimentally report the acoustic analogue of the super-Klein tunneling in a heterojunction of phononic crystals formed with Willis scatterers that exhibit pseudospin-1 Dirac cones. By comparing with the pseudospin-1/2 Dirac cones, pseudospin-1 ones require in the band structure an additional flatband across the Dirac points. The conventional Klein tunneling, which is predicted in pseudospin-1/2 systems like graphene, consists of perfect transmission only under normal incidence through a potential barrier of any width. However, the super-Klein tunneling that we evidence here is defined for pseudospin-1 systems as a perfect transmission for all incidence angles at one single frequency within the energy barrier. This direct observation may have important implications in the exploration of the rich physics of pseudospin-1 quasiparticles.

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