1.1 该测试方法包括使用一根管子、四个麦克风和数字频率分析系统，通过确定声学传递矩阵来测量材料的法向入射传输损耗和其他重要声学特性。 1.2 以国际单位制表示的数值应视为标准。本标准不包括其他计量单位。 1.3 本标准并不旨在解决与其使用相关的所有安全问题（如有）。本标准的使用者有责任在使用前制定适当的安全、健康和环境实践，并确定监管限制的适用性。 1.4 本国际标准是根据世界贸易组织技术性贸易壁垒委员会发布的《关于制定国际标准、指南和建议的原则的决定》中确立的国际公认的标准化原则制定的。 ====意义和用途====== 5.1 此测试有几个目的: 5.1.1 对于传输损耗: 一 以比试验方法更便宜、耗时更少的方法表征材料的隔音特性 E90 和ISO 140-3（“混响室方法”）， b 当较大的样品不可能构建或运输时，允许测试较小的样品， c 以实现不需要经验丰富的专业人员即可运行的快速技术。 5.1.2 对于传递矩阵: 一 以确定所述材料的附加声学特性； b 以允许通过组合它们各自的传递矩阵来计算组合材料或复合材料的声学特性。 5.2 这种方法与更传统的混响室方法有显著差异。 具体而言，与传统方法的随机入射相比，在这种方法中，声音仅沿垂直方向（“法线入射”）入射到样本上。此外，混响室方法规定了试样的某些最小尺寸，这可能不适用于所有材料。目前还不知道这两种方法之间的相关性（如果有的话）。尽管这种方法可能无法复制测量材料传输损耗的混响室方法，但它可以为小样本提供比较数据，这是混响室方法无法做到的。 在某些情况下，当材料被放置在靠近声源的小声腔内时，例如，紧密配合的机器外壳或便携式电子设备，正入射传输损耗也可能是有用的。 5.3 传输损耗不仅是材料的特性，而且在很大程度上取决于该方法固有的边界条件和材料安装方式的细节。在解释通过该试验方法获得的结果时，必须考虑到这一点。 5.4 这些量是作为频率的函数来测量的，其分辨率由数字频率分析系统的采样率、变换大小和其他参数确定。 可用的频率范围取决于管的直径和麦克风位置之间的间距。可以通过使用具有各种直径和麦克风间距的管来获得扩展的频率范围。 5.5 材料在声学系统元件中的应用可能与该测试方法不相似，因此通过该方法获得的结果可能与现场性能无关。

1.1 This test method covers the use of a tube, four microphones, and a digital frequency analysis system for the measurement of normal incident transmission loss and other important acoustic properties of materials by determination of the acoustic transfer matrix. 1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. 1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee. ====== Significance And Use ====== 5.1 There are several purposes of this test: 5.1.1 For transmission loss: (a) to characterize the sound insulation characteristics of materials in a less expensive and less time consuming approach than Test Method E90 and ISO 140-3 (“reverberant room methods”), (b) to allow small samples tested when larger samples are impossible to construct or to transport, (c) to allow a rapid technique that does not require an experienced professional to run. 5.1.2 For transfer matrix: (a) to determine additional acoustic properties of the material; (b) to allow calculation of acoustic properties of built-up or composite materials by the combination of their individual transfer matrices. 5.2 There are significant differences between this method and that of the more traditional reverberant room method. Specifically, in this approach the sound impinges on the specimen in a perpendicular direction (“normal incidence”) only, compared to the random incidence of traditional methods. Additionally, revereration room methods specify certain minimum sizes for test specimens which may not be practical for all materials. At present the correlation, if any, between the two methods is not known. Even though this method may not replicate the reverberant room methods for measuring the transmission loss of materials, it can provide comparison data for small specimens, something that cannot be done in the reverberant room method. Normal incidence transmission loss may also be useful in certain situations where the material is placed within a small acoustical cavity close to a sound source, for example, a closely-fitted machine enclosure or portable electronic device. 5.3 Transmission loss is not only a property of a material, but is also strongly dependent on boundary conditions inherent in the method and details of the way the material is mounted. This must be considered in the interpretation of the results obtained by this test method. 5.4 The quantities are measured as a function of frequency with a resolution determined by the sampling rate, transform size, and other parameters of a digital frequency analysis system. The usable frequency range depends on the diameter of the tube and the spacing between the microphone positions. An extended frequency range may be obtained by using tubes with various diameters and microphone spacings. 5.5 The application of materials into acoustical system elements will probably not be similar to this test method and therefore results obtained by this method may not correlate with performance in-situ.