电声乐器中木材声学振动性能对音响特性的影响

Effects of acoustic vibration properties of wood on acoustic characteristic in electronic musical instrument

电声乐器是现代科学技术的产物,在现代音乐中占有很重要的地位。电声弦乐器与传统弦乐器相比少了共鸣板(共鸣箱),而琴体部分多由实木构成。因这类乐器的发声原理特异而导致对使用的材料以及结构上的要求也有所变化。以电吉他为研究对象,通过对木材的振动声学性质以及电磁拾音器输出信号的音响特性进行研究,初步分析了在打击音法和拾音器集音的2种方式下对数衰减率和比动弹性模量之间的关系。结果表明,赤桦木最适合做为琴体材料;琴体在横向振动方式下的比动弹性模量约为纵向振动方式的24倍;拾音器所输出的泛音成分在3和5倍区域趋于集中。此外,进一步评价了琴体木材和琴弦振动对拾音器的影响,为继续深入探讨木材在电声乐器中的应用提供参考。

Electric musical instrument is the product of modern science and technology, which plays an important role in modern music. Compared with the traditional acoustic stringed instrument, the electric stringed instrument does not need a soundboard (resonator）, being made of solid wood for the instrument body. Due to the different vocalism prin- ciples, the requirements of material/structure are also different. In this paper, by taking the electric guitar as an exam- ple, the experimental method of the Tapping-Tone technique was adopted. The specific dynamic young＇s modulus and the logarithmic decrement of three kinds of wood species （Palaquium spp., Jaglans nigra and Alnus rubra）, and the electric guitar＇s electromagnetic pickup output of the logarithmic decrement of the time domain signals were deter~ mined. The acoustical vibration properties of the wood and the different acoustic characteristic of the pickup output sig- nais were investigated. When tapping-tone technique （the transverse vibration mode and the longitudinal vibration mode） and the magnetic pickup collect sound were used, the relationship between the logarithmic decrement ratio and specific dynamic elastic modulus, as well as the relationship between the specific dynamic modulus of wood and loga- rithmic decay rate of vibration in these species of trees were preliminarily analyzed. The results showed that A. rubra was the most suitable species for the body material of stringed instruments; under the transverse vibration mode, the dynamic elastic modulus of body was about 24 times higher than that of the longitudinal mode; the output overtone components tended to be concentrated in the area of 3 and 5 times from the pickup; the effect of the re-vibrations of the strings on the body was greater than the vibration of string-connection buttons or tuners. In addition, the influences of body wood and string vibration on the pickup were evaluated, which would provide further study with a reference on the application of wood in electroacoustic instruments.