水介质管路弹性背腔微穿孔消声器的传递损失特性

为抑制水介质管路系统低频噪声,兼顾结构的紧凑性,提出弹性背腔微穿孔管路消声结构,弹性管壁为橡胶帘线复合材料,并推导了传递损失的数值解法。首先,基于Biot-Allard多孔弹性理论,将弹性微穿孔板等效为弹性多孔材料;然后,利用双尺度法建立帘布的周期性代表单元,求得其刚度矩阵;接着,基于分层理论,建立弹性管壁的多层复合材料模型,并与内部声场耦合计算,得到弹性背腔微穿孔管路消声器的传递损失。在水介质驻波管中,利用双声源法测量弹性背腔微穿孔管路消声器样机的传递损失曲线,并与扩张式管路消声器和刚性背腔微穿孔管路消声器进行对比,理论结果与试验结果吻合良好。研究表明,弹性背腔微穿孔管路消声器属于反射耗散复合式消声器,具有低频域、宽频带的消声特性。样机B2在40~300 Hz和40~1200 Hz频段内的传递损失分别为36 dB和30 dB,而相同尺寸扩张式消声器在对应频段的传递损失分别为7 dB和11 dB。 

Transmission loss of flexible micro-perforated muffler with flexible back cavity for water filled pipelines

To reduce lowfrequency noise of the water filled pipeline system,a compact Flexible Micro-Perforated Muffler with Flexible Back Cavity(FMPMFBC) is proposed The flexible pipe wall is made up of rubber-cord composite material.Numerical solution for the transmission loss is derived.Firstly,the Flexible Micro-Perforated Panel(FMPP) is equivalent to a flexible porous material based on Biot-Allard porous-elastic theory.Then,a periodic structural unit of the aramid fabric cloth is established with two-scale method,and the equivalent stiffness matrix is obtained.Using the lamination theory,a multi-layer composite model for the flexible pipe wall is established.Coupling with internal sound field,the transmission loss of the FMPMFBC is calculated.On a water filled impedance tube the transmission loss curves of the FMPMFBC prototypes are measured with the two source-location method,and compared with those of flexible micro-perforated muffler with rigid back cavity and expansion muffler.Theoretical results are experimentally verified.The FMPMFBC,with broadband low-frequency noise attenuation characteristics,is a hybrid muffler combined reflection with dissipation.The transmission loss of prototype B2 in the frequency bands of 40-300 Hz and 40-1200 Hz are 36 dB and 30 dB,respectively.While the transmission loss of the same size expansion muffler in the corresponding frequency band are 7 dB and 11 dB respectively