1987 Fiscal Year Final Research Report Summary
Improvement of Acoustical Properties of Wood through Chemical Modification
| Project/Area Number |
61460213
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
林産学
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| Research Institution | Kyoto University |
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Principal Investigator |
NORIMOTO Misato Wood Research Institute, Kyoto University, Associate Professor, 木材研究所, 助教授 (20027163)
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| Co-Investigator(Kenkyū-buntansha) |
OHGAMA Toshimasa Faculty of Education, Chiba University, Associate Professor, 教育学部, 助教授 (60093209)
MINATO Kazuya Faculty of Agriculture, Kyoto Universuty, Instructor, 農学部, 助手 (10026601)
OKAMURA Keizo Faculty of Agriculture, Kyoto University, Professor, 農学部, 教授 (50026506)
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| Project Period (FY) |
1986 – 1987
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| Keywords | Acetylation / Formaldehyde Crosslinking / Musical Instrument / Dimensional Stability / Internal Friction / 内部摩擦 / ピアノピン板 |
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| Research Abstract |
To improve and stabilize tones of musical instruments made of wood such as piano and violin, it is very important for all the parts of the instruments to have good acoustical properties and dimesional stability. The aim of the study was to improve the acoustical properties such as specific Young's modulus and internal friction of wood and to suppress the creep deformation of wood under humidity changes through acetylation and formaldehyde crosslinking. Both the values of specific Young's modulus and internal friction decreased with increasing degree of acetylation. On the other hand, the value of specific Young's modulus decreased as the reaction time with formaldehyde increased in the longitudinal direction of wood but remained unchanged in the radial direction. The value of internal friction decreased in both the directions as the reaction time increased. The treatments reduced the amount of moisture changes and the corresponding variation of the acoustical properties. It is well known that the creep deformation of wood is greatly accelerated when humidity is changing. Both the treatments remarkably reduced the creep deformation. Formaldehyde crosslinking was more effective to suppress the deformation, but it was accompanied by color change and a pronounced reduction in the strength properties of wood. As an application, changes of the resonance frequency and tuning torque with humidity cycling were measured for full-scale models of the string-sustaining part at the 72th key with untreated wood block and acetylated wood block. Acetylation greatly reduced the changes of resonance frequency and suppressed decrease of the tuning torque. From these results, it was indicated that acetylation was effective to the treatment for the parts sustaining loads in the musical instruments, while formaldehyde crosslinking for soundboards.
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