The tongue is composed entirely of soft tissue: muscle, fat, and connective tissue. This unusual composition and the tongue’s 3D muscle fiber orientation result in many degrees of freedom. The lack of bones and cartilage means that muscle shortening creates deformations, particularly local deformations, as the tongue moves into and out of speech gestures. The tongue is also surrounded by the hard structures of the oral cavity, which both constrain its motion and support the rapid small deformations that create speech sounds. Anatomical descriptors and categories of tongue muscles do not correlate with tongue function as speech movements use finely controlled co-contractions of antagonist muscles to move the oral structures during speech. Tongue muscle volume indicates that four muscles, the genioglossus, verticalis, transversus, and superior longitudinal, occupy the bulk of the tongue. They also comprise a functional muscle grouping that can shorten the tongue in the x, y, and z directions. Various 3D muscle shortening patterns produce large- or small-scale deformations in all directions of motion. The interdigitation of the tongue’s muscles is advantageous in allowing co-contraction of antagonist muscles and providing nimble deformational changes to move the tongue toward and away from any position.
Marie K. Huffman
Articulatory phonetics is concerned with the physical mechanisms involved in producing spoken language. A fundamental goal of articulatory phonetics is to relate linguistic representations to articulator movements in real time and the consequent acoustic output that makes speech a medium for information transfer. Understanding the overall process requires an appreciation of the aerodynamic conditions necessary for sound production and the way that the various parts of the chest, neck, and head are used to produce speech. One descriptive goal of articulatory phonetics is the efficient and consistent description of the key articulatory properties that distinguish sounds used contrastively in language. There is fairly strong consensus in the field about the inventory of terms needed to achieve this goal. Despite this common, segmental, perspective, speech production is essentially dynamic in nature. Much remains to be learned about how the articulators are coordinated for production of individual sounds and how they are coordinated to produce sounds in sequence. Cutting across all of these issues is the broader question of which aspects of speech production are due to properties of the physical mechanism and which are the result of the nature of linguistic representations. A diversity of approaches is used to try to tease apart the physical and the linguistic contributions to the articulatory fabric of speech sounds in the world’s languages. A variety of instrumental techniques are currently available, and improvement in safe methods of tracking articulators in real time promises to soon bring major advances in our understanding of how speech is produced.