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发表于 2008-9-23 13:54:14
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What is ASTRA?
什么是ASTRA
The ASTRA projects aims to reconstruct the sound or timbre of ancient instruments (not existing anymore) using archaeological data as fragments from excavations, written descriptions, pictures...
ASTRA项目之目的在于，使用出土文物、书面描述、图片等考古资料片断，重现古代乐器(现已不再存在)的声音或音色。
The technique used is the physical modeling synthesis, a complex digital audio rendering technique which allows modeling the time-domain physics of the instrument.
使用了物理模型合成，一种综合数码音频演奏技术，形成乐器的时间域物理模型。
In other words the basic idea is to recreate a model of the musical instrument and produce the sound by simulating its behavior as a mechanical system. The application would produce one or more sounds corresponding to different configurations of the instrument (i.e. the different notes).
换言之，基本想法是重新建立乐器模型并模拟其作为机械系统之情形。该应用将制造相当于乐器的不同配置下的一或多个声音（也就是不同的音符）。
What is physical modeling?
什么是物理建模？
Physical modeling synthesis is the synthesis of sound by using a set of equations and algorithms to simulate a physical source of sound. Sound is then generated using parameters that describe the physical materials used in the instrument and the user's interaction with it, for example, by plucking a string, or covering tone holes, and so on. For example, to model the sound of a drum, there would be a formula for how striking the drumhead injects energy into a two dimensional membrane.
物理模拟合成是合成的声音用一套方程和算法，模拟实际来源的声音。声音由描述乐器所用物理材料以及使用者对乐器的动作（如弹拔琴弦、覆盖音孔等等）而产生。举例来说，对于模拟鼓声，将有一个公式阐明敲击鼓面加添能量到二维的膜。
Thereafter the properties of the membrane (mass density, stiffness, etc.), its coupling with the resonance of the cylindrical body of the drum, and the conditions at its boundaries (a rigid termination to the drum's body) would describe its movement over time and thus its generation of sound. Similar stages to be modeled can be found in instruments such as a violin, though the energy excitation in this case is provided by the slip-stick behavior of the bow against the string, the width of the bow, the resonance and damping behavior of the strings, the transfer of string vibrations through the bridge, and finally, the resonance of the soundboard in response to those vibrations.
Although physical modeling was not a new concept in acoustics and synthesis, having been implemented using finite difference approximations of the wave equation by Hiller and Ruiz in 1971, it was not until the development of the Karplus-Strong algorithm, the subsequent refinement and generalization of the algorithm into the extremely efficient digital waveguide synthesis by Julius O. Smith III and others, and the increase in DSP power in the late 1980s that commercial implementations became feasible.
（中间两段没兴趣翻译了，哪位帮一下，顺便校一下上面的错。特别是那个physical modeling我还没读完这两段，所以请读通后再重新考虑一下对应的中文词汇。THX）
Reason for gridification
网络计算之原因
Physical modeling is a really computing intensive technique since the complex models of the musical instruments are solved by integrating numerical coupled differential equations. To have an idea of the needed time for simulation, on a Pentium IV1.6 Ghz, 512MB RAM Personal Computer to correctly reproduce a sound lasting for 30 seconds it could be required more than 4 hours.
物理模拟确是一个计算密集的技术，因为复杂的模型的乐器是由integrating numerical coupled differential equations得以解决。为了更多的时间进行仿真，在奔腾IV1.6Ghz、512Mb内存的个人电脑，正确重现了一个持续的30秒的声音可能需要4个多小时。
ASTRA and GEANT2
ASTRA 和 GEANT2
ASTRA computations are quite demanding in terms of network and computing requirements. The extremely high reliability of the GEANT2 network, its performances in terms of number of institutions connected and thoughput, made the ASTRA project possible.
ASTRA计算有相当苛刻的网络和计算的条件的要求。极高可靠性的GEANT2网络， its performances in terms of number of institutions connected and thoughput，使ASTRA项目成为可能。
The project is running since 2006 thanks to the GEANT2 backbone, allowing researchers, musicians and historians to collaborate, communicate and share experiencies on lost instruments and sounds ASTRA brings again to life.
感谢GEANT2支柱，项目自2006年来一直在运行，允许研究人员、音乐家、历史学家进行合作、交流、分享 ASTRA重新带来的古乐器音
（英文来源:http://www.astraproject.org/index.html） |
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发表于 2008-9-23 14:38:16