| Project/Area Number |
14550466
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
土木材料・力学一般
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| Research Institution | University of Miyazaki |
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Principal Investigator |
NAKAZAWA Takao University of Miyazaki, Faculty of Engineering, Professor, 工学部, 教授 (70041027)
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| Co-Investigator(Kenkyū-buntansha) |
IMAI Fujio University of Miyazaki, Faculty of Engineering, Professor, 工学部, 教授 (00038077)
新西 成男 宮崎大学, 工学部, 助手 (00274770)
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| Project Period (FY) |
2002 – 2004
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| Project Status |
Completed (Fiscal Year 2004)
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| Budget Amount *help |
¥3,100,000 (Direct Cost: ¥3,100,000)
Fiscal Year 2004: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 2003: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 2002: ¥1,300,000 (Direct Cost: ¥1,300,000)
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| Keywords | porous Concrete / weighted equivalent continuous sound pressure level / normal incident absorption coefficient / type of aggregate / void content / 吸音率 / 吸音壁 / ぼら / 石灰石 / 残響室法吸音率 / 斜入射吸音率 |
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| Research Abstract |
Porous Concrete(PoC), which can be made by omitted fine aggregates or limit the content of fine aggregate in matrix, has some special functions such as pavement drainage, traffic noise reduction or planting due to its interconnected void structure. Experimental researches on noise absorption of PoC have been carried out in recent years. In order to develop a PoC that can reduce the traffic noise, a series of experiments to measure the normal incident sound absorption coefficient of PoC by impedance tube method have been conducted in our laboratory. How to reduce the weighted equivalent continuous sound pressure level (Leq) of a sound absorption wall made of PoC has also been studied.
This paper presents the experimental results on the sound absorption walls by using PoC. Aggregates used in these walls were lightweight pumice aggregate (PU), limestone aggregate (LS), and ferro-nickel slag aggregate(FNS). FNS is a by-product during the manufacture of ferro-nickel. Void content of PoC was
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designed as 20% and 30% in order to evaluate its influence on the sound absorption properties of PoC. Leq of the sound absorption wall measured by sound level meter at the frequency of 1/3 octave band from 100 to 2000 Hz was obtained. Normal incident absorption coefficients (αo) of specimen with a diameter of 95 mm bored from the sound absorption wall was measured by using an impedance tube. Relationship between Leq and ao was examined.
The following conclusions can be drawn from the experimental results.
1)The PoC wall made of FNS had the highest sound absorption capacity because of its smaller void size and lower void content than the other two PoC walls made of PU or LS.
2)Results of the influence of diffraction on decrease of Leq also showed that PoC wall made of FNS had the highest sound absorption capacity.
3)For the PoC wall made of PU or LS, sound energy transmitted through the void structure resulted in lower sound absorption capacity than that made of FNS. For the PoC wall made of PU or SL, at the frequency around 500Hz, which was corresponding to the first peak of sound absorption coefficient, decrease of Leq was not so large because sound energy transmitted through the void structure of PoC wall to the other side.
4)For PoC wall made of the same type of aggregate, Leq decreased with the decrease of void content. Less
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