A consonant produced by allowing the airstream to flow over the sides of the tongue
Answers
a) the airstream process--the source of air used in making the sound.
b) the phonation process--the behavior of the vocal cords in the glottis during the production of the sound.
c) the oro-nasal process--the modification of that flow of air in the vocal track (from the glottis to the lips and nose).
Let's discuss the airstream process first.
The airstream process
The first major way to categorize sounds according to phonetic features is by the source of air. Where does the air come from that is modified by the vocal organs? Languages can use any of three airstream mechanisms to produce sounds.
One airstream mechanism is by far the most important for producing sounds in the world's languages. Most sounds in the world's languages are produced by manipulating air coming into the vocal tract as it is being exhaled by the lungs, a method referred to as the pulmonic egressive airstream mechanism. Sounds made by manipulating air as it is exhaled from the lungs are called pulmonic egressive sounds. Virtually all sounds in English and other European languages are produced by manipulating exhaled air. And most sounds in other languages are also pulmonic egressive.
There is another variety of this pulmonic airstream mechanism. Inhaled air can also be modified to produce speech sounds. This actually occurs in a few rare and special cases, such as in Tsou, an aboriginal language of Taiwan, which has inhaled [f] and [h] ([h5/˝ps˝] ashes; [f5/tsuju], egg). Such sounds are called pulmonic ingressive sounds, and the airstream mechanism for making such sounds is called the ingressive rather than the egressive version of the pulmonic airstream mechanism. Perhaps because it is physiologically harder to slow down an inhalation than an exhalation, pulmonic ingressive sounds are extremely rare.
The majority of the sounds in all languages of the world are pulmonic egressive sounds. However, in addition to using air being actively exhaled (or inhaled), two other airstream mechanisms are used to produce some of the sounds in some of the world's languages.