含泡胶质体层的声透射特性研究

Acoustic transmission through a single layer of bubbly gel

对包含有限数目气泡的单层胶质体模型,在理论上研究了垂直入射的平面纵波的透射特性.利用计及多重散射效应的自洽场方法,严格求解了该模型中的声传播问题并得到了声透射系数.数值计算结果证明声波可在略高于气泡本征频率的频段内发生局域化,且局域化现象在气泡含量较小时已经出现.此外,采用等效媒质方法对该模型进行均匀化近似后求解了其声透射系数.在不同结构参数下,分析比较了两种方法所得结果的差异,考察了等效媒质方法的适用性.结果表明多重散射效应在气泡含量较低时已显著影响当前模型的声透射特性,尽管等效媒质方法在气泡含量极低(～10-5)时可简便的得到基本有效的计算结果,但当气泡含量变高(～10-4)时,忽略多重散射效应的等效媒质方法已不能正确的描述此类媒质的声传播特性.

For a single slab fabricated by elastic gel which contains randomly-distributed air bubbles, the propagation of normally-incident longitudinal plane wave is theoretically studied. The wave propagation is solved rigorously by using a selfconsistent method,with the multiple scattering effects fully incorporated. In a range of frequency slightly above the bubble resonance frequency,the acoustic localization in such a class of media is theoretically identified with even a very small volume fraction of bubbles. The sensibility of the features of localization to the structure parameters is numerically investigated. Comparisons are performed between the results obtained by using the effective medium method and selfconsistent method for different structure parameters. The results show that the multiple scattering is very important for bubbly gel even when the volume concentration of bubble is low. It is convenient to accurately describe the acoustic transmission in the present model by using effective medium method when the concentration is extremely low （-10^ 5）,but the effective medium method will fail to reveal some significant phenomena resulting from the multiple scattering effects as the concentration approximates 10 ^4.