A biomechanical modeling study of the effects of the orbicularis oris muscle and jaw posture on lip shape

TL;DR

This study uses biomechanical models to explore how variations in orbicularis oris muscle anatomy and jaw posture influence lip shapes and speech articulation, revealing biomechanical constraints on lip and jaw movements.

Contribution

It introduces a biomechanical modeling approach to analyze how anatomical differences affect lip gestures and jaw posture constraints in speech production.

Findings

Peripheral and moderately deep OO best for protrusion and rounding

Superficial OO facilitates lip closure

High jaw position needed for protrusion and rounding

Abstract

Purpose: The authors' general aim is to use biomechanical models of speech articulators to explore how possible variations in anatomical structure contribute to differences in articulatory strategies and phone systems across human populations. Specifically, they investigated 2 issues: (a) the link between lip muscle anatomy and variability in lip gestures and (b) the constraints of coupled lip/jaw biomechanics on jaw posture in labial sounds. Method: The authors used a model coupling the jaw, tongue, and face. First, the influence of the orbicularis oris (OO) anatomical implementation was analyzed by assessing how changes in depth (from epidermis to the skull) and peripheralness (proximity to the lip horn center) affected lip shaping. Second, the capability of the lip/jaw system to generate protrusion and rounding, or labial closure, was evaluated for different jaw heights. Results: Results showed that a peripheral and moderately deep OO implementation is most appropriate for protrusion and rounding; a superficial implementation facilitates closure; protrusion and rounding require a high jaw position; and closure is achievable for various jaw heights. Conclusions: Models provide objective information regarding possible links between anatomical and speech production variability across humans. Comparisons with experimental data will illustrate how motor control and cultural factors cope with these constraints.