Acoustical properties of farmland
Acoustical properties of farmland
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农田的声学特性
DOI：
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发表时间：
2000
期刊：
影响因子：
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通讯作者：
J. Lines
中科院分区：
文献类型：
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作者：
K. Attenborough;T. Waters;K. M. Li;J. Lines
尽管对声音在草原上的传播进行了许多测量，但在耕地表面上的数据相对较少。声音在吸收表面上的传播受到表面阻抗以及声源和接收器位置的影响。由于宽带声源靠近地面，接地阻抗的降低会增加 A 计权声级的衰减率。距点源 1 m 处的复杂过度衰减测量已用于推断包括耕地在内的各种农田表面的声阻抗。这些数据表明，农田表面的阻抗值比噪声预测方案中假设的典型草地覆盖表面的阻抗值低。给出了在四个耕作表面上距离扬声器 30 和 44 m 处的垂直分离麦克风测量的电平差的频谱。在深土或犁过的地面上测量的光谱与在相对未受干扰的表面上获得的光谱之间的差异与考虑粗糙多孔表面的有效阻抗的预测一致。研究发现，A 加权宽带声音在油菜作物上以及麦茬田中经过犁耕且未受干扰的部分（距离达 50 m）的衰减率大于经验 ISO 方法的预测值。发现使用单个地面参数的简单半经验模型与这些数据具有更好的一致性。
Although many measurements have been made of the propagation of sound over grassland, there are relatively few data over cultivated surfaces. The propagation of sound over an absorbing surface is influenced by the impedance of the surface and the locations of the source and the receiver. A reduction in ground impedance can increase the rate of attenuation of A-weighted sound levels due to broad-band sources near to the ground. Measurements of complex excess attenuation at 1 m from a point source have been used to deduce the acoustical impedance of a variety of farmland surfaces including arable land. These data suggest that farmland surfaces have lower impedance values than those assumed typical of grass-covered surfaces in noise prediction schemes. Spectra of the difference in levels measured at vertically separated microphones at distances of 30 and 44 m from a loudspeaker over four cultivated surfaces are presented. The differences between spectra measured over subsoiled or ploughed ground and those obtained over relatively undisturbed surfaces are consistent with predictions that take into account the effective impedance of rough porous surfaces. The rates of attenuation of A-weighted broad-band sound over an oilseed rape crop, and over ploughed and undisturbed portions of a wheat stubble field at ranges up to 50 m are found to be greater than predicted by an empirical ISO method. A simple semi-empirical model that uses a single ground parameter is found to give better agreement with these data.