边缘效应对于混响室法测量吸声系数影响的研究

发布时间：2018-10-07 18:48

【摘要】：随着我国逐渐步入小康社会,人们对于精神层次的需求越来越显著,建筑声学在生活中的影响越来越大。吸声材料作为降低噪声、改善声环境的有效材料,重要性不言而喻,而吸声系数则是评定吸声材料吸声性能的关键指标。对于材料吸声系数的测量有很多种方法,最能体现实际工程需求的是混响室法,然而在运用混响室法测量吸声系数时,由于存在实验设施和实验条件的非理想因素,导致其出现一定的问题：一是不同混响室对于同一材料吸声系数的测量值有时会出现很大偏差,以至于测量结果没有横向对比性；二是材料吸声系数的测量值随着材料面积、材料在室内位置及布置方式的改变而变化；三是对于一些强吸声材料测试,其中、高频段的吸声系数有可能大于1。本论文的研究工作主要是围绕材料吸声机理及试验材料的选择、混响室空场混响时间空间分布情况,以及边缘效应对于混响室法测量吸声系数的影响这三个方面来进行。第一,材料吸声机理及材料的选择。介绍了基本的声学理论,阐述了吸声材料的吸声机理,对比分析了几种吸声系数的测试方法,最后阐明为何要选择玻璃棉作为本次实验的测试材料。第二,混响室空场混响时间空间分布情况的研究。介绍室内声场的基本特征,阐明混响室测量混响时间过程中产生空间偏差的原因,通过大量测试空场状况下不同频率段混响时间,综合对比分析说明空间偏差对于混响室法测量吸声系数的影响。第三,边缘效应对于混响室法测量吸声系数的影响。在标准混响室内,通过混响室内设置的升降平台的上下移动,可以得到材料表面高出或与地面平齐等不同情况,以达到存在或基本消除试件边缘效应的效果,对比研究可得到不同状况下相应的混响时间,计算出在不同情况下的吸声系数。研究发现,对于玻璃棉来说,在高频段上的边缘效应边界散射现象使得其吸声系数有所提高,但不是导致吸声系数大于1的唯一因素。从总体上来看,边缘效应边界散射现象的影响是有限的,而边界阻抗突变可能对于中频有很大影响。
[Abstract]:As our country gradually steps into a well-off society, people's demand for spiritual level is more and more obvious, and architectural acoustics has more and more influence in life. As an effective material for reducing noise and improving sound environment, the sound absorption material is important, and the sound absorption coefficient is the key index to evaluate the sound absorption performance of the sound absorption material. There are many methods for measuring the sound absorption coefficient of materials. The reverberation chamber method is the most effective method for measuring the sound absorption coefficient of materials. However, when the reverberation chamber method is used to measure the sound absorption coefficient, there are some non-ideal factors such as experimental facilities and experimental conditions. It causes some problems: first, the measurement value of the sound absorption coefficient of the same material in different reverberation chambers sometimes deviates greatly, so that the measured results do not have a transverse contrast; the other is that the measured value of the sound absorption coefficient of the material varies with the area of the material. Thirdly, for some strong sound absorption materials, the sound absorption coefficient of high frequency range may be greater than 1. The research work of this paper mainly focuses on three aspects: the sound absorption mechanism of materials and the selection of test materials, the distribution of reverberation time and space in the empty field of reverberation chamber, and the influence of edge effect on the measurement of sound absorption coefficient by reverberation chamber method. First, the sound absorption mechanism of materials and the selection of materials. This paper introduces the basic acoustic theory, expounds the sound absorption mechanism of the sound absorbing material, compares and analyzes several measuring methods of the sound absorption coefficient, and finally explains why the glass cotton should be selected as the testing material in this experiment. Second, the study of time and space distribution of reverberation in reverberation chamber. This paper introduces the basic characteristics of indoor sound field, clarifies the causes of spatial deviation in the measurement of reverberation time in reverberation chamber, and through a large number of measurements of reverberation time in different frequency segments under the condition of empty field, The influence of spatial deviation on the measurement of sound absorption coefficient by reverberation chamber method is explained by comprehensive comparative analysis. Thirdly, the effect of edge effect on the sound absorption coefficient measured by reverberation chamber method. In the standard reverberation room, by moving up and down of the lifting platform set up in the reverberation chamber, different situations such as the material surface is higher or level with the ground can be obtained, so as to achieve the effect of the existence or the basic elimination of the edge effect of the specimen. The reverberation time under different conditions can be obtained by comparative study, and the sound absorption coefficient under different conditions can be calculated. It is found that the edge effect boundary scattering phenomenon in the high frequency band increases the sound absorption coefficient of glass cotton, but it is not the only factor leading to the sound absorption coefficient greater than 1. In general, the effect of edge effect boundary scattering phenomenon is limited, and the boundary impedance mutation may have a great influence on intermediate frequency.
【学位授予单位】：中国建筑科学研究院
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TU552;TU112

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