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5.1 The main part of this standard uses procedures originally developed for laboratory measurements of the transmission loss of partitions. These procedures assume that the rooms in which the measurements are made have a sound field that reasonably approximates a diffuse field. Sound pressure levels in such rooms are reasonably uniform throughout the room and average levels vary inversely with the logarithm of the room sound absorption. Not all rooms will satisfy these conditions. Practical experience and controlled studies (1)6 have shown that the test method is applicable to smaller spaces normally used for work or living, such as rooms in multi-family dwellings, hotel guest rooms, meeting rooms, and offices with volumes less than 150 cubic meters. The measures appropriate for such spaces are NR, NNR, and ATL. The corresponding single number ratings are NIC, NNIC and ASTC. The ATL and ASTC may be measured between larger spaces that meet a limitation on absorption in the spaces to provide uniform sound distribution.
5.2 Annex A2 was developed for use in spaces that are very large (volume of 150 m3 or greater). Sound pressure levels during testing can vary markedly across large rooms so that the degree of isolation can vary strongly with distance from the common (separating) partition. This procedure evaluates the isolation observed near the partition. The appropriate measure is NR, and the appropriate single number rating is NIC.
5.3 It is sometimes necessary to demonstrate that the sound insulation of a partition meets or exceeds a specific criterion. Annex A1 provides additional requirements, and describes how shielding procedures can be used to reduce flanking transmission in stages to show that a partition has achieved a minimum value of the FTL or minimum value of the FSTC which may meet or exceed the criterion. If it is demonstrated that no significant flanking exists through shielding of all potential flanking paths, then, and only then, FTL and FSTC may be reported without qualification.
Note 3: Measuring the sound transmission loss properties of a partition itself to demonstrate that it meets or exceeds a specific criterion is very difficult in the field due to the presence of flanking (2, 3). Room volume and absorption requirements must also be met.
5.4 Several metrics are available for specific uses. Some evaluate the overall sound isolation between spaces including the effect of absorption in the receiving space and some evaluate the performance or apparent performance of the partition being evaluated. The results obtained are applicable only to the specific location tested.
5.4.1 Noise Reduction (NR) and Noise Isolation Class (NIC)—Describe the sound isolation found between the two spaces under consideration. Noise reduction data are based on the space- and time averaged sound pressure levels meeting the requir......<......
符合ASTM D3985标准的库仑检测法透氧仪,即Labthink兰光生产的C230氧气透过率测试系统,C230是一款专业、、智能的氧气透过率测试仪,适用于不同材质的薄膜、片材、纸张、容器及其他类似材料的氧气透过性能测试。 技术特征:1、专业——采用高精度氧变送器,使用Labthink独有的核心控制技术,隔绝外界干扰并保持极低信号衰减,在极宽的测试范围内实现高分辨率和高灵敏度的氧测量能力。...
与距离 r 平方成反比) Lpi——第i个噪声源在受声点P出的声级; Lwi——第i个噪声源的声功率级; Lp总——受声点P出的总声级; ΔL1——噪声随传播距离的衰减; ΔL2——噪声被空气吸收的衰减; ΔL3——墙壁屏障效应衰减; ΔL4——户外建筑物屏障效应衰减; ΔL5——植物吸收效应衰减; ΔL6——阻挡物的反射效应衰减。 ...
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