Articulatory Phonetics

The field of articulatory phonetics is a subfield of phonetics. In studying articulation, phoneticians explain how humans produce speech sounds via the interaction of different physiological structures.

Generally, articulatory phonetics is concerned with the transformation of aerodynamic energy into acoustic energy. Aerodynamic energy refers to the airflow through the vocal tract. Its potential form is air pressure; its kinetic form is the actual dynamic airflow. Acoustic energy is variation in the air pressure that can be represented as sound waves, which are then perceived by the human auditory system as sound.

The vocal tract can viewed through an aerodynamic-biomechanic model that includes three main components:

1. air cavities
2. pistons
3. air valves

Air cavities are containers of air molecules of specific volumes and masses. The main air cavities present in the articulatory system are the supraglottal cavity and the subglottal cavity. They are so-named because the glottis, the openable space between the vocal folds internal to the larynx, separates the two cavities. The supraglottal cavity or the orinasal cavity is divided into an oral subcavity (the cavity from the glottis to the lips excluding the nasal cavity) and a nasal subcavity (the cavity from the velopharyngeal port, which can be closed by raising the velum to the nostrils). The subglottal cavity consists of the trachea and the lungs. The atmosphere external to the articulatory stem may also be consisted an air cavity whose potential connecting points with respect to the body are the nostrils and the lips.

Pistons are initiators. The term initiator refers to the fact that they are used to initiate a change in the volumes of air cavities, and, by Boyle's Law, the corresponding air pressure of the cavity. The term initiation refers to the change. Since changes in air pressures between connected cavities lead to airflow between the cavities, initiation is also referred to as an airstream mechanism. The three pistons present in the articulatory system are the larynx, the tongue body, and the physiological structures used to manipulate lung volume (in particular, the floor and the walls of the chest). The lung pistons are used to initiate a pulmonic airstream (found in all human languages). The larynx is used to initiate the glottalic airstream mechanism by changing the volume of the supraglottal and subglottal cavities via vertical movement of the larynx (with a closed glottis). Ejectives and implosives are made with this airstream mechanism. The tongue body creates a velaric airsteam by changing the pressure within the oral cavity: the tongue body changes the mouth subcavity. Click consonants use the velaric airstream mechanism. Pistons are controlled by various muscles.

Valves regulate airflow between cavities. Airflow occurs when an air valve is open and there is a pressure difference between in the connecting cavities. When an air valve is closed, there is no airflow. The air valves are the vocal folds (the glottis), which regulate between the supraglottal and subglottal cavities, the velopharyngeal port, which regulates between the oral and nasal cavities, the tongue, which regulates between the oral cavity and the atmosphere, and the lips, which also regulate between the oral cavity and the atmosphere. Like the pistons, the air valves are also controlled by various muscles.