Narrow Results

Complex structures, large size and limited manipulation of acoustic waves are the problems that restrict the development of acoustic metasurfaces. Here, we report a transmission-type acoustic metasurface based on local resonance mechanism, which is composed of meta-atomic units called dumbbell-shaped double-split hollow spheres (DSDSHS). This metasurface with subwavelength scale has the advantage of simple structure and easy preparation, and can realize the full manipulation of sound waves. Negative refraction with different transmission angles and high intensity plate focusing lens are realized in the air environment of audible frequency. The proposed metasurface has potential applications in the miniaturization and integration of sound transmission and sound energy collection, opening a new opportunity for manipulation of acoustic wavefront.

A kind of acoustic metasurface (AMS) with multiple response frequency bands based on the replace method was proposed, which composed of six units, each containing three split hollow cubics (SHCs) (denoted as the AAA type of AMS). The simulation results demonstrated that the presented AMS can achieve the flexible modulation of the reflected wave direction. The AAA type of AMS had one response band, the AAC type of AMS had two different response bands, and the ABC type of AMS had three different response bands. Furthermore, the response bandwidth of the ABC type of AMS declined the most in the middle-frequency band, followed in the low-frequency band, and the least in the high-frequency band, when compared to the corresponding AAA type of AMS with single bandwidth. In addition, it was worth noting that the ABC type of AMS not only enlarged the manipulation direction of reflected acoustic wave, but also improved the effects of the wavefront distribution at the same frequency. This multiple band AMS will be beneficial for the application of architectural acoustics, and acoustic absorption and noise reduction.

An acoustic metasurface (AM) is proposed to achieve a sound tunnel with switchable functionalities of asymmetric transmission and bidirectional sound isolation, which is composed of an array of steel containers filled with two inert gases, argon and xenon. Acoustic asymmetric transmission can be observed when the AM is placed vertically. The functionality of the tunnel can be switched to bidirectional sound isolation by simply rotating the AM without changing the physical structure of the device. The proposed switchable tunnel has broadband multi-functional response with a simple adjustment method, showing potential for bidirectional sound isolation and sound sensing.