Howe M S, McGowan R S
Boston University, College of Engineering, 110 Cummington Street, Boston MA 02215.
J Fluids Struct. 2009 Nov 1;25(8):1299-1317. doi: 10.1016/j.jfluidstructs.2009.08.002.
An analysis is made of the nonlinear interactions between flow in the subglottal vocal tract and glottis, sound waves in the subglottal system and a mechanical model of the vocal folds. The mean flow through the system is produced by a nominally steady contraction of the lungs, and mechanical experiments frequently involve a 'lung cavity' coupled to an experimental subglottal tube of arbitrary or ill-defined effective length L, on the basis that the actual value of L has little or no influence on excitation of the vocal folds. A simple, self-exciting single mass mathematical model of the vocal folds is used to investigate the sound generated within the subglottal domain and the unsteady volume flux from the glottis for experiments where it is required to suppress feedback of sound from the supraglottal vocal tract. In experiments where the assumed absorption of sound within the sponge-like interior of the lungs is small, the influence of changes in L can be very significant: when the subglottal tube behaves as an open-ended resonator (when L is as large as half the acoustic wavelength) there is predicted to be a mild increase in volume flux magnitude and a small change in waveform. However, the strong appearance of second harmonics of the acoustic field is predicted at intermediate lengths, when L is roughly one quarter of the acoustic wavelength. In cases of large lung damping, however, only modest changes in the volume flux are predicted to occur with variations in L.
对声门下声道中的气流与声门之间的非线性相互作用、声门下系统中的声波以及声带的力学模型进行了分析。通过肺部名义上的稳定收缩产生通过该系统的平均气流，并且力学实验通常涉及一个“肺腔”与一个有效长度L任意或定义不明确的实验性声门下管相连，基于L的实际值对声带的激发几乎没有影响这一观点。一个简单的、自激单质量声带数学模型被用于研究在需要抑制来自声门上声道的声音反馈的实验中，声门下区域内产生的声音以及声门处不稳定的体积通量。在假设肺部海绵状内部对声音的吸收较小的实验中，L的变化的影响可能非常显著：当声门下管表现为开口端谐振器时（当L大到声波波长的一半时），预计体积通量大小会有轻微增加，波形会有小的变化。然而，当L约为声波波长的四分之一时，预计在中等长度时声场的二次谐波会强烈出现。然而，在肺部阻尼较大的情况下，预计随着L的变化，体积通量只会有适度变化。
