Fractal Acoustic Metamaterials with Subwavelength and Broadband Sound Insulation

Abstract

We construct new fractal acoustic metamaterials by coiling up space, which can allow subwavelength-scale and broadband sound insulation to be achieved. Using the finite element method and the S-parameter retrieval method, the band structures, the effective parameters, and the transmission losses of these acoustic metamaterials with different fractal orders are researched individually. e results illustrate that it is easy to form low-frequency bandgaps using these materials and thus achieve subwavelength-scale sound control. As the number of fractal orders increase, more bandgaps appear. In particular, in the ΓX direction of the acoustic metamaterial lattice, more of these wide bandgaps appear in different frequency ranges, thus providing broadband sound insulation and showing promise for use in engineering applications.

Design of flat broadband sound insulation metamaterials by combining Helmholtz resonator and fractal structure

“…It means that it can form as much surface as possible in a design area. Therefore, there are many cases applied to the field of electromagnetic metamaterials to improve absorption performance, and there are a few cases applied to acoustic metamaterials [25,28].…”

“…Sound insulation method based on the energy absorption of a medium through channel extension such as a fractal structure is suitable for flattening the sound insulation characteristics of broadband frequency [28]. However, there is a limitation that the sound insulation effect according to the expansion channel is insignificant at low frequencies below 1000 Hz.…”