We demonstrate a high-efficiency sound-absorbing metasurface operating at low frequency. The metasurface absorber is based on acoustic porous layer embedded two identical but oppositely oriented split tube resonators. A high absorption (>50%) is obtained in a frequency range from 170 Hz to 750 Hz and over 90% absorption exhibits from 285 Hz to 340 Hz, while the thickness of the absorber is only 1/6 of the relevant wavelength at 500 Hz. The broadband and high absorption performances are due to the coupling of the resonance modes and the trapped mode. Furthermore, the high-efficiency low-frequency absorption of the metasurface is robust under oblique incidence even at large angles. The absorber is ease of fabrication, subwavelength thickness, and robust high-efficiency. Therefore, it has high potential applications in noise control and architectural acoustics.
