Fractal acoustic metamaterial based broadband acoustic focusing lens and preparation method thereof

The invention discloses a fractal acoustic metamaterial based broadband acoustic focusing lens and a preparation method thereof. The broadband acoustic focusing lens comprises a base material and a fractal structure unit array located on the base material. The fractal structure unit array is formed by arranging a plurality of fractal periodic units, and each fractal periodic unit corresponds to a refraction point of the focusing lens. The fractal period unit comprises a fractal unit and air, and a refractive index of the fractal unit corresponding to any refraction point conforms to a theoretical refractive index of the refraction point. According to the invention, the fractal units are adopted for the first time to form the acoustic focusing lens, thereby providing a new way for designing a new material for the acoustic engineering. The actual path length of spreading of acoustic waves in a unit structure is increased in a fractal mode, and the refractive index of the unit structure is improved. The acoustic