一维亥姆霍兹共振腔声子晶体中缺陷模式的实验研究

Experiments on defect mode of one-dimensional phononic crystal containing Helmholtz resonators

基于亥姆霍兹共振腔单元设计并制作了一种一维局域共振型声子晶体,针对结构中存在点缺陷的情况,进行了实验研究.实验结果表明,由于点缺陷的存在,局域共振型声禁带中出现了缺陷模式,并且在缺陷单元周围引起了能量的局域现象,与理论结果符合较好.缺陷单元从两个不同的方向趋近于完美单元时,缺陷模式分别按照不同的规律变化,但是越靠近禁带边缘,所局域的能量就越多.另外,当缺陷单元共振频率小于完美单元共振频率时,局域能量主要集中在声波导内;反之,局域能量则主要集中在共振腔内.本研究对设计新型低频声滤波装置及高声强集中装置具有一定意义.

In this paper, a local resonant phononic crystal is designed and fabricated based on Helmholtz resonators. Experiment is carried out to study the defect mode of the structure, in which a point defect is introduced. Due to the coupling of the defect cell and perfect cells, a narrow pass band appears in the local resonant forbidden band. Meanwhile, acoustic energy localization effect is observed around the defect resonator at the frequency of defect mode which changes with the defect parameter. However, the defect mode is close to the edge of the forbidden band, the localized energy is high. In addition, if the resonant frequency of the defect unit is smaller than that of the perfect unit, the localized energy is mostly distributed in the waveguide. In contrast, the energy is mostly localized in the resonators when the defect unit frequency is larger than that of the perfect unit. This work will be of help for designing new acoustic functional devices of filters and concentrators.