Near-perfect low-frequency sound absorption in subwavelength H-fractal metamaterials

Abstract We designed and demonstrated the near-perfect low-frequency sound absorption in subwavelength H-fractal metamaterials, in which the absorption peak frequency can be continuously tuned by changing the opening positions. Moreover, the total thickness of the acoustic metamaterial can be decreased to λ /92.2 by increasing the number of openings. The underlying mechanism is ascribed to the impedance matching due to additional couplings from new openings. The experimental results agree well with the numerical analyses, and the proposed method provides a new route for reducing the thickness of sound-absorbing materials, which may find large application demands in the noise control field.