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Based on the modification of the radial pulsation equation of an individual bubble, an effective medium method (EMM) is presented for studying propagation of linear and nonlinear longitudinal acoustic waves in viscoelastic medium permeated with air bubbles. A classical theory developed previously by Gaunaurd (Gaunaurd GC and UEberall H, J. Acoust, Soc, Am., 1978; 63: 1699-1711) is employed to verify the EMM under linear approximation by comparing the dynamic (i.e. frequency-dependent) effective parameters, and an excellent agreement is obtained. The propagation of longitudinal waves is hereby studied in detail, The results illustrate that the nonlinear pulsation of bubbles serves as the source of second harmonic wave and the sound energy has the tendency to be transferred to second harmonic wave, Therefore the sound attenuation and acoustic nonlinearity of the viscoelastic matrix are remarkably enhanced due to the system's resonance induced by the existence of bubbles. 相似文献
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The propagation of longitudinal acoustic waves in weakly compressible elastic media permeated with air bubbles is investigated on the basis of the radial pulsation equation of a single bubble. The multiple scattering of waves in such media is rigorously described by using a self-consistent approach. Theoretical results show that there exists strong acoustic localization in a range of frequency slightly above the bubble resonance frequency, even for a very small volume fraction of bubbles. Further study reveals that the localization is in fact attributed to collection behaviour of bubbles, allowing for an efficient cancellation of propagating waves. This is essentially consistent with the known conclusions recently drawn for bubbly liquid by Kou et al. [2003 Appl. Phys. Left. 83 4247] 相似文献
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利用对墙截面形状的优化来改善声学小房间的低频响应 总被引:2,自引:2,他引:0
提出了通过优化墙截面形状来改变声学小房间低频响应的优化方法。在矩形有限元模型中将墙面用不同的阶梯形状作为墙截面进行代换,并用于具有不同墙面的房间,进行了声场分析。阶梯形状间的差异仅是阶梯高度的取值不同,分别为相等、随机和优化值。将获得优化值的优化方法用于60Hz到120Hz的频率范围内,对不同阶梯墙面以及平墙面房间的频率响应进行了数值计算和比较。结果显示墙截面采用优化值时得到的房间频响最为均匀;将房间长、宽、高比例改变后重复上述数值分析,仍得到房间频响改善在优化情况下最大的结果。对比例较差的房间改善幅度可达4.5dB。另外还以半圆和三角形作为墙截面形状计算了半圆半径和三角形高度分别为固定值和优化值时房间的频率响应,同样得到优化墙面优于固定值墙面的结果。因此通过运用优化的墙截面来改善房间低频声场特性是有意义的。 相似文献
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含气泡水的强非线性声学特性 总被引:3,自引:0,他引:3
本文提出一种描述含气泡水的非线性声场的物理模型。在声波驱动下,气泡壁作受迫振动,遵循Rayleigh-Plesset方程,当共振时振幅很大,产生强烈的非线性振动。这非线性力学振动成为二次谐波声压的源,从而声场表现为强非线性。理论计算与WU和Zhu的实验结果进行了比较,诸如强二次谐波声压等重要声学特性符合得比较满意。 相似文献