弦乐器指板常用热带硬阔叶木材的声学振动性能分析  

Acoustic Vibration Analysis of Tropical Hardwoods for Fretboard of String Musical Instrument

作　　者：刘美宏[1] 彭立民[1] 吕少一[1] 吕建雄[1] 高玉磊 樊正强 Liu Meihong;Peng Limin;Lü Shaoyi;Lü Jianxiong;Gao Yulei;Fan Zhengqiang(Key Laboratory of Wood Science and Technology of National Forestry and Grassland Administration Research Institute of Wood Industry, CAF Beijing 100091)

机构地区：[1]中国林业科学研究院木材工业研究所国家林业和草原局木材科学与技术重点实验室,北京100091

出　　处：《林业科学》2021年第6期125-133,共9页Scientia Silvae Sinicae

基　　金：国家重点研发计划项目“木材材质改良的物理与化学基础”(2017YFD0600202)。

摘　　要：【目的】分析弦乐器指板常用热带硬阔叶木材的声学振动性能,归纳总结指板用木材的声学振动性能要求,为寻找可替代树种或对人工林木材进行功能改良以替代传统指板用木材提供科学依据。【方法】采用X-射线剖面密度测试仪表征木材一个生长轮内早晚材的密度差异及沿径向密度分布的均匀性;利用超声波微秒计测试木材声传播速度;运用模态分析法测试木材的共振频率和扭转频率,根据矩形截面Euler-Bernoulli方程计算木材声学振动参数。【结果】乌木绝干密度为1180 kg·m^(-3),阔叶黄檀绝干密度为810 kg·m^(-3),东非黑黄檀绝干密度为1320 kg·m^(-3);弦乐器共鸣板用硬槭木绝干密度为660 kg·m^(-3),非乐器用木材辐射松绝干密度为480 kg·m^(-3)。乐器用木材一个生长轮内早晚材及相邻生长轮之间密度差异较小,材质均匀。指板用木材轴向和径向声传播速度均低于硬槭木和辐射松。硬槭木顺纹与横纹的声传播速度比为3.2,声学各向异性较优。乌木、东非黑黄檀和阔叶黄檀的动态弹性模量(E′)分别为18.2、16.8和14.8 GPa,指板用木材的E′均大于14.0 GPa。指板用木材的比动态弹性模量(Esp)均小于18.0 GPa,硬槭木和辐射松的Esp分别为24.5和26.8 GPa,均高于指板用木材。乌木、阔叶黄檀和东非黑黄檀的声辐射品质常数(R)分别为3.21、5.08和2.58 m^(3)·Pa^(-1)s^(-3),硬槭木和辐射松的R分别为7.17和9.41 m3·Pa^(-1)s^(-3)。指板用木材的声阻抗(ω)、对数衰减系数(λ)和损耗角正切值(tanδ)均高于硬槭木和辐射松。指板用木材的声学转化率(ACE)和E′/G′均低于硬槭木。乌木、阔叶黄檀、东非黑黄檀、硬槭木和辐射松的动态剪切模量(G′)分别为1.97、1.72、2.58、1.21和1.09 GPa,指板用木材的G′均大于硬槭木和辐射松。【结论】指板用木材绝干密度均大于800 kg·m^(-3)。木材密度与其声学振动性能存在一定函�【Objective】The acoustic vibration properties of commonly used string musical fretboard wood were comprehensive analyzed and summarized,which could be the basis for the search of alternative wood or modification of fast-growing wood.【Method】The X-ray profile densitometer was used to characterize the density differences between the earlywood and latewood in a growing ring and their uniformities along the radial density distribution.The ultrasonic microsecond meter was used to test the sound propagation speed of the wood.The vibration frequency,torsional frequency and damping ratio of wood were tested by modal analysis method.The acoustic vibration performance parameters of wood were also calculated according to the Euler-Bernoulli equation of rectangular section.【Result】The oven dry density of fretboard wood was 1180 kg·m^(-3)for ebony(Diospyros crassiflora),810 kg·m^(-3)for Indian rosewood(Dalbergia latifolia),1320 kg·m^(-3)for African blackwood(Dalbergia melanoxylon),660 kg·m^(-3)for the hardwood hard maple(Acer saccharum)string instrument soundboard and 480 kg·m^(-3)for non-instrumental wood radiata pine,respectively.The density differences of fretboard wood between the earlywood and latewood in the growth ring and between the adjacent growth ring were not significant,and had a uniform texture.The sound propagation velocity of the fretboard wood was lower than that of hard maple and radiata pine in axial and radial direction.The sound propagation speed ratio of parallel grain to vertical grain of hard maple was 3.2,which was the maximum value.The acoustic anisotropy of hard maple was much better.The dynamic modulus of elasticity(E′)of ebony,African blackwood and Indian rosewood were 18.2,16.8 and 14.8 GPa,respectively,which indicated that the dynamic modulus of elasticity of fretboard wood was greater than 14.0 GPa.The specific dynamic modulus of elasticity(Esp)of fretboard wood was less than 18.0 GPa,those of hard maple and radiata pine were 24.5 and 26.8 GPa,respectively,which were all highe

关 键 词：弦乐器 指板 共鸣板 声学振动性能 

分 类 号：S781.38[农业科学—木材科学与技术]