UCLA School of Medicine, 31-24 Rehabilitation Center, 1000 Veteran Avenue, Los Angeles, California 90095-1794, USA.
J Acoust Soc Am. 2011 Apr;129(4):2163-7. doi: 10.1121/1.3543989.
Negative damping and eigenmode synchronization as two different mechanisms of phonation onset are distinguished. Although both mechanisms lead to a favorable phase relationship between the flow pressure and the vocal fold motion as required for a net energy transfer into the vocal folds, the underlying mechanisms for this favorable phase relationship are different. The negative damping mechanism relies on glottal aerodynamics or acoustics to establish before onset and maintain after onset the favorable phase relationship, and therefore has minimum requirements on vocal fold geometry and biomechanics. A single degree-of-freedom vocal fold model is all that is needed for self-oscillation in the presence of a negative damping mechanism. In contrast, the mechanism of eigenmode synchronization critically depends on the geometrical and biomechanical properties of the vocal folds (at least 2-degrees-of-freedom are required), and has little requirement on the glottal aerodynamics other than flow separation. The favorable phase relation is established once synchronization occurs, regardless of the phase relationship imposed by glottal aerodynamics before onset. Unlike that of the negative damping mechanism, initiation of eigenmode synchronization requires neither a velocity-dependent flow pressure nor an alternating convergent-divergent glottis. The clinical implications of the distinctions between these two mechanisms are discussed.
负阻尼和本征模同步作为两种不同的发声起始机制被区分开来。尽管这两种机制都导致流压和声带运动之间形成有利于净能量传递到声带的相位关系，但这种有利相位关系的潜在机制是不同的。负阻尼机制依赖于声门气流动力学或声学在起始前建立并在起始后维持有利的相位关系，因此对声带几何形状和生物力学的要求最小。在存在负阻尼机制的情况下，单自由度声带模型足以实现自激振荡。相比之下，本征模同步的机制严重依赖于声带的几何形状和生物力学特性（至少需要 2 个自由度），并且除了气流分离之外，对声门气流动力学的要求很少。一旦发生同步，有利的相位关系就会建立，而不管起始前声门气流动力学施加的相位关系如何。与负阻尼机制不同的是，本征模同步的启动既不需要依赖于速度的流压，也不需要交替的收束-扩张的声门。讨论了这两种机制之间的区别的临床意义。
