Effective impedance spectra for predicting rough sea effects on atmospheric impulsive sounds.
Effective impedance spectra for predicting rough sea effects on atmospheric impulsive sounds.
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用于预测波涛汹涌的海面对大气脉冲声音的影响的有效阻抗谱。
DOI：
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发表时间：
2005
影响因子：
2.4
通讯作者：
K. Attenborough
中科院分区：
文献类型：
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作者：
P. Boulanger;K. Attenborough
探索了两种计算声硬、随机粗糙、二维表面有效阻抗谱的方法，这些表面的声波波长比粗糙度尺度大。第一种方法利用边界元法（BEM）预测的粗糙边界上点源的复过量衰减谱，用圈数积分法求解有效阻抗根。第二种方法是基于解析理论，将表面散射体随机分布的贡献相加得到总散射场。通过测量由半圆柱形和楔形组成的二维随机粗糙表面上的复杂多余衰减，推导出有效阻抗谱，并与两种方法的预测结果进行了比较。虽然解析理论给出的预测相对较差，但bem推导出的有效阻抗谱与实测数据相当吻合。对于平均粗糙度高度在0.25 ~ 7.5 m之间、每个平均高度对应5个入射角的相交抛物线所形成的表面，发现可以用简单多项式拟合边界元法推导出的光谱。海面粗糙度对音爆剖面和上升时间的预测影响与湍流和分子松弛效应的预测结果相当。
Two methods of calculating the effective impedance spectra of acoustically hard, randomly rough, two-dimensional surfaces valid for acoustic wavelengths large compared with the roughness scales have been explored. The first method uses the complex excess attenuation spectrum due to a point source above a rough boundary predicted by a boundary element method (BEM) and solves for effective impedance roots identified by a winding number integral method. The second method is based on an analytical theory in which the contributions from random distributions of surface scatterers are summed to obtain the total scattered field. Effective impedance spectra deduced from measurements of the complex excess attenuation above 2D randomly rough surfaces formed by semicylinders and wedges have been compared to predictions from the two approaches. Although the analytical theory gives relatively poor predictions, BEM-deduced effective impedance spectra agree tolerably well with measured data. Simple polynomials have been found to fit BEM-deduced spectra for surfaces formed by intersecting parabolas corresponding to average roughness heights between 0.25 and 7.5 m and for five incidence angles for each average height. Predicted effects of sea-surface roughness on sonic boom profiles and rise time are comparable to those due to turbulence and molecular relaxation effects.