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为了研究不同顶端形态声屏障对噪声衍射的衰减特性,针对4种常见的声屏障噪声衰减问题,应用菲涅尔半波带法,对其插入损失进行计算并对其降噪效果进行评价。充分考虑次级扰动带来的半波带声能贡献,推导任意阶半波带声屏障声影区的衍射衰减计算公式。通过计算4种不同顶端形态下声屏障的插入损失,绘制不同声屏障下交通噪声的衍射声场,并呈现其水平和垂直方向的噪声衍射规律。计算结果表明,声屏障的插入损失随着高度和离声屏障距离的增加而减小。顶端形态对声屏障降噪效果有很大影响,其中T型和Y型屏障对声音遮挡最为明显,其次为折角型屏障,竖直型屏障降噪效果最差。试验结果验证了4种声屏障的衍射规律,并进一步证实了存在双衍射现象的T型和Y型屏障有更明显的降噪效果。
In order to study the attenuation characteristics of noise diffraction of different top morphological sound barriers, four FNB noise attenuation problems are studied. The Fresnel half-band method is used to calculate the insertion loss and to evaluate the noise reduction effect. Considering the contribution of the half-band sound energy caused by the secondary disturbance, the diffraction attenuation formula of the acoustic shadow zone in any order half-waveband is deduced. By calculating the insertion loss of the sound barrier under four different top configurations, the diffraction sound field of traffic noise under different sound barriers is plotted, and the horizontal and vertical diffraction patterns of noise are presented. The calculation results show that the insertion loss of the acoustic barrier decreases with the increase of the height and the distance from the acoustic barrier. The shape of the top has a great influence on the noise reduction effect of the sound barrier, of which the T-type and Y-type barriers have the most obvious sound obstruction, followed by the angle-type barrier, and the vertical type has the worst noise reduction effect. The experimental results verify the diffraction patterns of the four kinds of sound barriers and further confirm that the T-type and Y-type barriers with double diffraction have a more obvious noise reduction effect.