Computer-Implemented Articulatory Models for Speech Production: A Review.

Bernd J Kröger

doi:10.3389/frobt.2022.796739

Abstract

Modeling speech production and speech articulation is still an evolving research topic. Some current core questions are: What is the underlying (neural) organization for controlling speech articulation? How to model speech articulators like lips and tongue and their movements in an efficient but also biologically realistic way? How to develop high-quality articulatory-acoustic models leading to high-quality articulatory speech synthesis? Thus, on the one hand computer-modeling will help us to unfold underlying biological as well as acoustic-articulatory concepts of speech production and on the other hand further modeling efforts will help us to reach the goal of high-quality articulatory-acoustic speech synthesis based on more detailed knowledge on vocal tract acoustics and speech articulation. Currently, articulatory models are not able to reach the quality level of corpus-based speech synthesis. Moreover, biomechanical and neuromuscular based approaches are complex and still not usable for sentence-level speech synthesis. This paper lists many computer-implemented articulatory models and provides criteria for dividing articulatory models in different categories. A recent major research question, i.e., how to control articulatory models in a neurobiologically adequate manner is discussed in detail. It can be concluded that there is a strong need to further developing articulatory-acoustic models in order to test quantitative neurobiologically based control concepts for speech articulation as well as to uncover the remaining details in human articulatory and acoustic signal generation. Furthermore, these efforts may help us to approach the goal of establishing high-quality articulatory-acoustic as well as neurobiologically grounded speech synthesis.

Highlights

An articulatory model is a quantitative computer-implemented emulation or mechanical replication of the human speech organs
In this paper we focus on computer-implemented models beginning with models developed in the 1960s/1970s up to contemporary articulatory models and synthesizers which are developed to approach the goal of producing high-quality articulatory-acoustic signals and/or to reproduce the neuromuscular and biomechanical properties of articulators as close as possible
One of the main problems in developing articulatory models is the lack in articulatory data exhibiting a sufficient spatiotemporal resolution

Summary

INTRODUCTION

An articulatory model is a quantitative computer-implemented emulation or mechanical replication of the human speech organs. It can be extended towards an articulatory-acoustic model if in addition an acoustic speech signal is produced based on the geometrical information provided by the articulatory model. The term articulatory model will include articulatory-acoustic models in this paper. The speech organs modeled in these approaches can be divided in sub-laryngeal, laryngeal, and supra-laryngeal organs. The sub-laryngeal system comprising lungs and trachea provides subglottal pressure and sufficient airflow for speaking, the laryngeal system provides the phonatory signal (primary source signal), and the supra-laryngeal system comprising pharyngeal, oral, and nasal cavities and comprising the articulators for modifying the shape of the pharyngeal and

Articulatory Models for Speech Production

Major goal

CVC movement data extracted from literature

Findings

LIMITATIONS AND FUTURE DIRECTIONS FOR MODELING SPEECH ARTICULATION