Dipartimento di Energetica, Termofluidoidinamica applicata e Condizionamenti Ambientali, Università di Napoli Federico II, piazzale Tecchio 80, 80125 Napoli, Italy.
J Acoust Soc Am. 2011 Feb;129(2):753-64. doi: 10.1121/1.3523433.
Air-flow resistivity is a main parameter governing the acoustic behavior of porous materials for sound absorption. The international standard ISO 9053 specifies two different methods to measure the air-flow resistivity, namely a steady-state air-flow method and an alternating air-flow method. The latter is realized by the measurement of the sound pressure at 2 Hz in a small rigid volume closed partially by the test sample. This cavity is excited with a known volume-velocity sound source implemented often with a motor-driven piston oscillating with prescribed area and displacement magnitude. Measurements at 2 Hz require special instrumentation and care. The authors suggest an alternating air-flow method based on the ratio of sound pressures measured at frequencies higher than 2 Hz inside two cavities coupled through a conventional loudspeaker. The basic method showed that the imaginary part of the sound pressure ratio is useful for the evaluation of the air-flow resistance. Criteria are discussed about the choice of a frequency range suitable to perform simplified calculations with respect to the basic method. These criteria depend on the sample thickness, its nonacoustic parameters, and the measurement apparatus as well. The proposed measurement method was tested successfully with various types of acoustic materials.
空气流阻是影响多孔吸声材料声学性能的主要参数。国际标准 ISO 9053 规定了两种测量空气流阻的方法，即稳态气流法和交流气流法。后者通过在部分封闭测试样品的小刚性体积中测量 2 Hz 时的声压来实现。该腔室由已知体积速度声源激励，通常使用带有预定面积和位移量的电机驱动活塞进行激励。2 Hz 的测量需要特殊的仪器和注意。作者提出了一种基于通过传统扬声器耦合的两个腔室中测量的高于 2 Hz 频率的声压比的交流气流方法。基本方法表明，声压比的虚部可用于评估空气流动阻力。讨论了选择适合简化基本方法计算的频率范围的标准。这些标准取决于样品厚度、其非声学参数以及测量设备。所提出的测量方法已成功用于各种类型的吸声材料。
