超材料型周期管路声传播特性及低频宽带控制
Sound propagation characteristics of a metamaterials-type periodic pipe and its low-frequency broadband control
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摘要: 船舶管路系统噪声的低频宽带控制是船舶设计和制造中亟待解决的关键问题之一。将超材料理论引入船舶管路系统的结构设计,构造了具有低频声波带隙的一维周期管路结构,并给出了周期管路声波带隙和声波透射系数的计算方法。计算结果表明,该周期管路同时存在声波布拉格带隙和局域共振带隙。在这两种带隙频率范围内,声波在系统中的传播将被衰减抑制。进一步发现,布拉格和局域共振带隙在一定条件会发生耦合,出现带隙耦合展宽现象,且两种带隙存在精确耦合条件。利用带隙耦合的展宽效应和低频设计,可实现声波在低频范围内的传播操控,从而达到船舶管路系统低频噪声宽带控制的目的。Abstract: Control of low-frequency noise for piping system of ships is an urgently task that needs to be solved during the design and fabrication for new ships. Introducing the theory of acoustic metamaterials (AMs) into the structure design of pipe system of ships, a 1D periodic pipe structure with low-frequency band gaps (BGs) is constructed. Calculation methods for tile acoustic BGs and the coefficients of transmission waves are developed to conduct the investigation. Calculational results show that the Bragg and locally resonant (LR) BGs are simultaneously existed in the periodic pipe. Within these two two BGs, acoustic wave propagation in the system will be stopped. Further, these two types of BGs could be coupled under certainly condition, such that a broader BG is generated. Moreover, the coupling condition for Bragg and LR BGs could be exactly formulated. Utilizing the character of coupled BG and the low-frequency design, the propagation of acoustic wave can be manipulated in desired low frequency range, thus rendering the control of low-frequency noise in a broad range feasible.