多层声学覆盖层复合的有限长弹性圆柱壳声辐射特性研究

针对水下双层圆柱壳内外壳体各表面敷设隔声阻尼层的情况,建立了有限长多层复合加实肋板的双层圆柱壳水下声辐射计算模型.对模型采用模态展开法,系统考虑壳体与隔声层和实肋板耦合,外表面声学覆盖层作用和外部声场耦合,并以状态矢量对应的矩阵形式导出复合壳体辐射声功率的计算表达式.数值计算了隔声阻尼层和外场声学覆盖层层参数,实肋板参数和壳体阻尼对模型辐射声功率的影响.研究结果表明:有实肋板时阻尼层的降噪量最高接近15dB,实肋板的声短路作用限制了隔声阻尼层的降噪效果;双层隔声阻尼层比单层隔声阻尼层降噪效果好3-4dB.外场声学覆盖层受实肋板影响较阻尼层小,其降噪量达10dB左右.

Sound radiation of finite composite cylindrical shells with multi-layers acoustic coating

A model of composite finite cylindrical shells with acoustic coating on the external surface of inner shell and the double surfaces of outer shell is established,which has annular ribbed plates between the two shells.Mode expanding method is used to get the sound radiation power of the model,in which the coupling of the shells and the coating layers is taken into account,and as well the reaction of the anechoic tiles to the outer shell.The analytical expression of sound radiation power,which is formed by matrix equation,is obtained.The influence of the characteristic parameter of the coating layers,the ribbed annular plates and the anechoic tiles on the sound radiation power is discussed.The results show that the coating results in the sound radiation power reduction reaches up to 15dB in some frequency band,the ribbed annular plates result in sound short circuit and somewhat diminishes the effect of the acoustic coating;when there are two layers of acoustic coating,the sound radiation power is lower,about 3-5dB than that of single layer;the effect of anechoic tiles is more independent to the ribbed annular plates than the coating layer,the sound radiation power reduction caused by anechoic tiles is about 10dB.