Wideband acoustic modeling of speech

语音和歌唱的声学特性主要是在5千赫以下的低频下研究的，而较高的频率被认为基本上是无关的。然而，最近出现的证据表明，语音的高频成分发挥着比之前认为的更重要的作用，并携带例如副语言信息。目前关于语音的高频成分、它们的方向性相关的辐射以及它们与发音的关系的知识相当有限，部分原因是它们的研究困难。研究这些问题的一种潜在的合适方法是基于声道的宽带3D声学模拟。然而，当前的3D模拟方法要么计算非常昂贵(例如，有限元方法)，要么需要高度简化的声道几何结构(多模法)。在这里，我们提出了一种混合方法，用于声道的3D声学模拟，它覆盖了整个可听频率范围，并且同时具有快速和物理上的准确性。其基本思想是将解析多模态法与数值二维有限元法相结合来计算模态基函数。这种混合声学模型是在发音语音合成器vocalTractLab的框架下实现和优化的，在那里它与现有的声道3D发音模型相结合，以实现物理上准确的宽带连接语音合成。该方法通过对3D打印的声道复制品的宽带声学测量进行客观评估，并通过与人类听者的感知测试进行主观评估。

The acoustic properties of speech and singing have been mainly studied at low frequencies of up to 5 kHz, while higher frequencies have been considered essentially irrelevant. More recently, however, evidence has emerged that the high-frequency components of speech play a more significant role than previously believed, and carry, for example, paralinguistic information. The current knowledge about the high-frequency components of speech, their directivity-dependent radiation, and their relation to articulation are rather limited, partly due to the difficulties of their investigation. A potentially suitable approach to study these issues is based on the wideband 3D acoustic simulation of the vocal tract. However, current 3D simulation methods are either computationally very expensive (e.g., finite element methods), or require strongly simplified geometries of the vocal tract (multimodal method). Here, we propose the development of a hybrid method for the 3D acoustic simulation of the vocal tract that covers the whole audible frequency range and is fast and physically accurate at the same time. The basic idea is to combine the analytical multimodal approach with a numerical 2D finite element approach to compute the modal basis functions. This hybrid acoustic model is implemented and optimized in the framework of the articulatory speech synthesizer VocalTractLab, where it is combined with an existing 3D articulatory model of the vocal tract for the physically accurate wideband synthesis of connected speech utterances. The proposed method is evaluated objectively by means of wideband acoustic measurements of 3D-printed replicas of the vocal tract, and subjectively by a perception test with human listeners.