Development of surface area meter utilizing reverberation time

利用混响时间的表面积计的开发

• 批准号: 15360221
• 负责人: TORIGOE Ippei
• 金额: $ 7.36万
• 依托单位: Kumamoto University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 2003
• 资助国家: 日本
• 起止时间: 2003 至 2004
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-15360221/
• 关键词: Surface area; Reverberation time; Acoustic impedance; Diffusive sound field; 吸音率; 気密; マイクロホン; ノイズ断続法

The reverberation time of a room is in inverse proportion to the inner surface area of the room provided the sound field therein is diffuse. On the basis of this principle, the surface area of an object can be known from the measurement of the reverberation time of a container in which the object is placed. An experimental device was built on a trial basis which has the scaled-down dimensions of an actual reverberation room. A band noise is transmitted into the container from speakers and the sound pressure is picked up by condenser microphones. Using a noise switching method, the reverberation time of the container in which various sample objects were placed was measured. The experimental results showed the following : (i)the surface area of objects made of a material which absorbs sound moderately could be known from the reverberation time, (ii)the sound field within the container was not sufficiently diffuse in spite of the shape of the container ; (iii)the reverberation time of the container was affected by a slight change in the leak and the surrounding conditions, such as the atmospheric temperature and pressure. As to objects made of highly reflective material, it was known from another experiment that a method measuring the acoustic impedance of the container would work well. A new apparatus is afoot which is elaborated to attain a fully diffuse sound field and to eliminate the effect of the leak and the atmospheric temperature and pressure.

如果房间内的声场是扩散的，那么房间的混响时间与房间的内表面积成反比。根据这一原理，可以通过测量放置物体的容器的混响时间来知道物体的表面积。一个实验装置是在试验的基础上建造的，其尺寸缩小到了实际混响室的尺寸。频带噪声从扬声器传输到容器中，并由电容式麦克风接收声压。使用噪声切换方法，测量了放置各种样品对象的容器的混响时间。实验结果表明：(I)从混响时间可以知道由适度吸声的材料制成的物体的表面积；(Ii)无论容器的形状如何，容器内的声场都不是充分扩散的；(Iii)容器的混响时间受到泄漏和周围条件(如大气温度和压力)的轻微变化的影响。至于由高反射材料制成的物体，从另一项实验中得知，一种测量容器声阻抗的方法可以很好地工作。一种新的装置正在研制中，该装置旨在获得完全扩散的声场，并消除泄漏以及大气温度和压力的影响。