The word ‘airstream’ refers to a current of air; specifically ‘airflow’. The method by which airflow is created in the vocal tract is called airstream mechanism. Encyclopedia Britanica Dictionary (2010). The organ that generates the airstream is called the initiator and the production of airflow is called initiation. There are three initiators which are used in spoken human language, namely the diaphragm, the glottis and the tongue and these are linked to the following airstream mechanisms: * Pulmonic * Glottalic * Velaric
There are two types of airflow directions namely the egressive; whereby air is pushed out of the mouth through the vocal tract (the air passages above the larynx) and the ingressive whereby air is sucked into the vocal tract through the mouth during part of the articulation. The parts of the vocal tract that can be used to form sounds are called articulators. Ladefoged (1993).
The Pulmonic airstream mechanism is the mother body of all human languages. It is initiated by the respiratory muscles of the lungs. During this process, the air is pushed out of the lungs by the respiratory muscles creating an egressive type of airflow. The speech sound or stop made with this type of mechanism is plosive and it can either be voiced or voiceless. When a sound is voiced, the glottis (the space between the vocal chords) will slightly be adjusted, leaving a narrow passage between the chords; for air to pass through. The airstream will cause the chords to vibrate. Examples of such sounds are