高溫處理對阿拉斯加雲杉之平板振動性質之影響

Effect of High-temperature Treatment on the Plate Vibration Properties of Sitka Spruce

周琬喻(Wan-Yu Chou) ； 羅盛峰(Sheng-Fong Lo) ； 卓志隆(Chih-Lung Cho)

《林產工業》 35卷4期 (2016/12) Pp. 193-202

https://doi.org/10.6561/FPI.2016.35(4).2

摘要

長久以來雲杉屬木材即是重要的樂器用材，主要作為絃樂器的面板、鋼琴響板等用途。唯近年來優良音響用雲杉材料逐漸短缺且價格高昂，因此如何提昇低品質用材的音響性質，已成為重要的課題。本研究透過模態分析量測平板振動中（1,1）、（2,0）及（0,2）之共振頻率，探討130°C 及150°C 高溫處理對阿拉斯加雲杉徑面板材振動性質之影響。試驗結果顯示，經高溫處理之試材平衡含水率較未處理材為低，可顯著改善木材的吸濕性。縱向、徑向彈性模數及剪斷模數，有增加的趨勢，而縱向、徑向彎曲振動之內部摩擦皆有減低的趨勢。經130°C 高溫處理後之試材比動彈性模數、聲音輻射率及響度指數之增加率較經150°C 者為高，可獲得較良好的聲音品質。

關鍵字

阿拉斯加雲杉 ； 高溫處理 ； 平板振動 ； 音響性質

並列摘要

Wood of the Picea genus has been used as the material for the manufacturing of musical instrument since ancient time. It was primarily used for the top plate of stringed instruments and sounding board of piano. Improvement of the acoustic properties of low quality wood for musical instruments is very important. This would solve a problem originating in the short supply and expensive cost of high quality wood for musical instruments. This study aims to improve the acoustical quality of quarter-sawn Sitka spruce plate by using high-temperature treatment. Resonant frequencies of modes (1,1), (0,2), and (2,0) were determined by modal analysis to evaluate the effects of 130°C and 150°C treatment on the vibration properties of wooden plate.The experimental results showed that the equilibrium moisture contents of high-temperature treated specimens were lower than those of untreated specimens. The hygroscopic ability of high-temperature treated Sitka spruce was reduced significantly. An increase in modulus of elasticity along longitudinal and radial direction, shear modulus in LR section of specimens were observed after high-temperature treatment. The internal friction of longitudinal and radial flexural and torsional vibrations of specimens were reduced after high-temperature treatment. The percentage increases in specific dynamic modulus of elasticity, sound radiation ratio, and acoustic conversion loudness indexof 130°C treated specimens were greater than those after 150°C treatment. This reveals Sitka spruce plate could lead to a better sound quality after 130°C treatment.

並列關鍵字

Sitka spruce (Picea sitchensis) ； High-temperature treatment ； Plate vibration ； Acoustical properties