Periodic gradient duplexcavity meta-lens for wide-band directional acoustic beaming

Abstract Selective multi-directional sound projection across a wide-band low mid-frequency range remains a significant challenge in acoustic applications, primarily due to the manipulation of long wavelengths within compact acoustic meta-lens. This study introduces a novel directional acoustic beaming theoretical method, specifically a duplexcavity four-lobe valve-shaped acoustic meta-lens (DFVAM). By manipulating geometric parameters, the DFVAM effectively controls downstream acoustic in a directional sound projection fashion that enhances sound wave propagation across multiple wide frequency bands. Experimental results validate substantial sound focusing at frequencies of 4500–4800 Hz, 7200–7600 Hz, 9700–10 300 Hz, and 11 400–11 600 Hz, achieving sound beam lengths between 12 and 21 λ , cross-sectional areas ranging from 0.7 to 2 λ , and FWHM values of 0.140–0.218 m. This meta-lens offers efficient acoustic modulation and focusing across various frequency ranges, presenting promising applications in acoustic directional transmission, sound energy collecting and acoustic levitation.