Variability of vowel formants due to the finite impedances of the glottis, the velopharyngeal port, and the vocal tract walls

元音共振峰的频率通常被认为主要由声道的空腔形状决定，其带宽由各种损失机制决定，如软壁、粘性摩擦和嘴唇的声音辐射。然而，一些研究表明，共振峰的频率也受到某些边界条件的很大影响，特别是发声过程中声门的有限声阻抗，声道的软壁，以及不完全的腭咽闭合。所有这三种机制的效果都是相似的：前两个共振峰被移到更高的频率，它们的带宽变得更大(与具有硬壁的声道、完全关闭的声门和完全关闭的腭咽闭合口相比)。到目前为止，这三种机制只被单独考虑，而且大多使用语音设备的物理模型或使用计算机模拟(而不是人类)。该项目的目标是通过将受试者的实验与物理声道模型和计算机模拟相结合来更详细地研究这些机制。特别令人感兴趣的是，在改变共振峰的过程中，多个并发机制是如何相互作用的，它们共同的物理原因是什么，这些影响在多大程度上是感知相关的，以及它们是否以及如何被有意地用于演讲或唱歌。该项目的结果将允许更好地解释测量的共振峰频率，改进根据共振峰频率估计声道长度或声道形状的方法，改进反滤波方法，以及更准确的语音产生模拟模型。

Vowel formant frequencies are often thought to be determined primarily by the cavity shape of the vocal tract, and their bandwidths by various loss mechanisms such as the soft walls, viscous friction, and sound radiation from the lips. However, several studies suggest that formant frequencies are also considerably affected by certain boundary conditions, in particular by the finite acoustic impedance of the glottis during phonation, by the soft walls of the vocal tract, and by incomplete velopharyngeal closure. The effect of all three mechanisms is similar: the first two formants are shifted to a higher frequency and their bandwidths become larger (compared to a vocal tract with rigid walls, a fully closed glottis, and a fully closed velopharyngeal port). So far, the three mechanisms have only been considered individually, and mostly using physical models of the speech apparatus or using computer simulations (rather than humans). The goal of the project proposed here is to study these mechanisms in more detail by combining experiments on subjects, with physical vocal tract models, and computer simulations. Of particular interest is how multiple concurrent mechanisms interact in shifting the formants, what their common physical cause is, to what extent the effects are perceptually relevant, and whether and how they are intentionally used in speech or singing. The results of the project would allow, among other things, a better interpretation of measured formant frequencies, improvement of methods for estimating vocal tract length or vocal tract shape from formant frequencies, improvement of inverse filtering methods, and more accurate simulation models of speech production.