A simplified vocal tract model for articulation of [s]: The effect of tongue tip elevation on [s]

Fricative consonants are known to be pronounced by controlling turbulent flow inside a vocal tract. In this study, a simplified vocal tract model was proposed to investigate the characteristics of flow and sound during production of the fricative [s] in a word context. By controlling the inlet flow rate and tongue speed, the acoustic characteristics of [s] were reproduced by the model. The measurements with a microphone and a hot-wire anemometer showed that the flow velocity at the teeth gap and far-field sound pressure started oscillating before the tongue reached the /s/ position, and continued during tongue descent. This behaviour was not affected by the changes of the tongue speed. These results indicate that there is a time shift between source generation and tongue movement. This time shift can be a physical constraint in the articulation of words which include /s/. With the proposed model, we could investigate the effects of tongue speed on the flow and sound generation in a parametric way. The proposed methodology is applicable for other phonemes to further explore the aeroacoustics of phonation.

擦音辅音（fricative consonants）的发声过程通过调控声道（vocal tract）内的湍流流动实现。本研究提出一种简化声道模型，用以探究单词语境下擦音[s]发声过程中的流动与声学特性。通过控制入口流速与舌部运动速度，该模型成功复现了[s]的声学特征。借助麦克风与热线风速仪（hot-wire anemometer）开展的测量结果显示：齿间隙处的流动速度与远场声压，在舌部到达/s/发音位置前便已开始振荡，并在舌部回落过程中持续存在；且该振荡行为不受舌部运动速度变化的影响。上述结果表明，声源产生与舌部运动之间存在时间偏移，该偏移可成为包含/s/的单词在发音时的物理约束条件。借助所提出的模型，本研究能够以参数化方式探究舌部运动速度对流动与声产生过程的影响。本研究提出的方法可推广至其他音素（phonemes），以进一步探索发声的气动声学（aeroacoustics）特性。