The Didjeridu: Lip Motion and Low Frequency Harmonic Generation

L. Hollenberg
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引用次数: 8

Abstract

The dynamic acoustics of the Australian didjeridu are studied by separately considering transverse and longitudinal lip vibration models in the context of highly non-sinusoidal lip motion. Timedomain computer simulations are performed based on these lip models coupled to the input impedance function of a straight pipe. For the purposes of direct comparison, detailed results are reported here for lip motion leading to both sinusoidal lip opening area functions (characteristic of higher frequency brass instruments) and the more complex non-sinusoidal (approximately half-closed cycle) case characteristic of the didjeridu. Over a range of lip resonance frequencies, the sounding frequency for the transverse (longitudinal) model is found to be below (above) both the lip and fundamental pipe resonance frequencies, in qualitative agreement with linear theory for these value types. A striking difference is found between the two models when comparing the effect of significant lip closure in the non-sinusoidal cycle—the sounding frequency in the transverse case is raised by up to 10%, whilst essentially unaltered in the longitudinal model. The effect the lips sticking during the non-sinusoidal cycle was considered by increasing the damping force upon closure, and was found in both transverse and longitudinal models to weaken significantly the generation of harmonics in the sound.
Didjeridu:唇部运动与低频谐波的产生
在高度非正弦唇部运动的背景下,分别考虑横向和纵向唇部振动模型,研究了澳大利亚didjeridu的动态声学。将这些唇形模型与直管的输入阻抗函数耦合,进行了时域计算机仿真。为了直接比较,这里报告了唇部运动导致正弦唇部开口面积函数(高频铜管乐器的特征)和更复杂的didjeridu非正弦(大约半封闭周期)情况特征的详细结果。在唇形共振频率范围内,发现横向(纵向)模型的探测频率低于(高于)唇形和基管共振频率,在定性上与这些值类型的线性理论一致。当比较非正弦周期中显著的唇闭合的影响时,两个模型之间发现了显著的差异——横向情况下的探测频率提高了10%,而在纵向模型中基本上没有改变。在非正弦周期中,通过增加闭合时的阻尼力来考虑唇贴的影响,并且发现在横向和纵向模型中都显著削弱了声音中谐波的产生。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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