“同管双笛”本征频率的理论分析

Analysis about eigenfrequencies of aligned double flute

本文改进并推广了原有的横笛频率计算理论，使它适用于一种新颖的横笛──“同管双笛”。文中运用声在管道中传播的成熟理论，对双笛中的声学特性作了严格的分析。导出了计算双笛本征频率的理论关系式。讨论了吹孔末端修正及吹气温度的影响。以两种典型双笛结构为实例作了验证，理论计算与实测结果良好相符。表明本文所提供的理论准确可靠，可作为实际设计、制作双笛的重要依据。

In this paper, an improved theory for determining cigenfrequencis of flute is demonstrated. The theory is developed from author's previous work in order that it can be applied as well as to analyse the flute of a new type, such as the so-called 'aligned double flute'. The acoustic character of the double flute is analysed rigorously. The procedure to calculate the correction of the effective length of the tube at exit terminal is investigated. Theoretical formulas to determine eigenfrequencies of the double flute are derived. Correction at blow aperture and the influence of temperature deviation caused by the warm blow are discussed.Two typical structures of the double flute are illustrated. It is shown that experimental results are in good agreement with the theoretical calculation. It shows that the theory proposed in the present paper is delicate and reliable. It can serve as a theoretical fundamental for design or manufacture of the double flute in practice