Otsuru Toru, Tomiku Reiji, Din Nazli Bin Che, Okamoto Noriko, Murakami Masahiko
Department of Architecture and Mechatronics, Oita University, Oita, Japan.
J Acoust Soc Am. 2009 Jun;125(6):3784-91. doi: 10.1121/1.3125327.
An in-situ measurement technique of a material surface normal impedance is proposed. It includes a concept of "ensemble averaged" surface normal impedance that extends the usage of obtained values to various applications such as architectural acoustics and computational simulations, especially those based on the wave theory. The measurement technique itself is a refinement of a method using a two-microphone technique and environmental anonymous noise, or diffused ambient noise, as proposed by Takahashi et al. [Appl. Acoust. 66, 845-865 (2005)]. Measured impedance can be regarded as time-space averaged normal impedance at the material surface. As a preliminary study using numerical simulations based on the boundary element method, normal incidence and random incidence measurements are compared numerically: results clarify that ensemble averaging is an effective mode of measuring sound absorption characteristics of materials with practical sizes in the lower frequency range of 100-1000 Hz, as confirmed by practical measurements.
提出了一种材料表面法向阻抗的原位测量技术。它包括“总体平均”表面法向阻抗的概念，该概念将获得的值的使用扩展到各种应用，如建筑声学和计算模拟，特别是基于波动理论的应用。测量技术本身是对高桥等人[《应用声学》66, 845 - 865 (2005)]提出的使用双传声器技术和环境背景噪声或扩散环境噪声的方法的改进。测量得到的阻抗可视为材料表面的时空平均法向阻抗。作为基于边界元法的数值模拟的初步研究，对垂直入射和随机入射测量进行了数值比较：结果表明，总体平均是在100 - 1000 Hz低频范围内测量实际尺寸材料吸声特性的有效方式，实际测量也证实了这一点。
