Development of a measurement method for oblique-incidence absorption coefficient based on modal analysis in a thin chamber

2016 Fiscal Year Final Research Report

• Project/Area Number: 15K14072
• Research Category: Grant-in-Aid for Challenging Exploratory Research
• Allocation Type: Multi-year Fund
• Research Field: Architectural environment/Equipment
• Research Institution: The University of Tokyo
• Principal Investigator: Sakuma Tetsuya 東京大学, 大学院新領域創成科学研究科, 准教授 (80282995)
• Research Collaborator: INOUE Naohisa 東京大学, 大学院新領域創成科学研究科, 特任研究員 (00755803)
• Project Period (FY): 2015-04-01 – 2017-03-31
• Keywords: 建築音響 / 吸音率 / 音響測定 / 音響材料

Outline of Final Research Achievements

Regarding absorption coefficient measurement for acoustic materials, the reverberation room method for random incidence and the acoustic tube method for normal incidence have been standardized. In this study, a new measurement method for oblique-incidence absorption coefficient was proposed based on multi-point measurement and mode analysis. A prototype system was developed and test measurements were done for a variety of glass wool with different density, thickness and back air layer. The measured results were in good accordance with theoretical estimates, where the frequency- and incidence-angels-dependence of absorption coefficient were confirmed. However, it was found that abnormal values appear at specific combinations of frequency and incidence angle, which results from geometrical relationship of the loudspeaker position and normal modes. For avoiding the defect, an improvement point in the system was clarified.

Free Research Field

建築音響学