The branch of linguistics that deals with the sounds of speech and their production, combination, description, and representation by written symbols. Touching upon physics and physiology, phonetics is now a pure science that studies speech processes, including the anatomy, neurology and pathology of speech, the articulation, transmission, and perception of speech sounds.
Phonetics is divided into three main branches, corresponding to these three distinctions:
1. Articulatory phonetics is the study of the way the vocal organs are used to produce speech sounds.
2. Acoustic phonetics is the study of the physical properties of speech sounds.
3. Auditory phonetics is the study of the way people perceive speech sounds.
1. Articulatory 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.
In this sub-field of phonetics, phoneticians discuss production of speech sounds and classify them according to the place and manner of their production.
The major categories into which articulatory phonetics divides speech sounds are stops, fricatives and vowels. These terms refer to the degree of constriction that is imposed on their air stream. In ‘stops’ (plosives), no air at all may pass out of the vocal tract because the passage is completely blocked off at some point. In ‘fricatives’, there is a considerable narrowing of the passage which results in audible friction. Finally, if the vocal passage is almost unrestricted, the resulting sound is called ‘vowel’.
2. Acoustic Phonetics
Acoustic phonetics is a subfield of phonetics which deals with acoustic aspects of speech sounds. Acoustic phonetics investigates properties like the mean squared amplitude of a waveform, its duration, its fundamental frequency, or other properties of its frequency spectrum, especially as analyzed by means of instruments like the sound spectrograph and the oscillograph and the relationship of these properties to other branches of phonetics (e.g. Articulatory or Auditory phonetics).
When we speak we disturb the molecules in the air around us. These molecules oscillate, that is, they move back and forth rather like the swing of a pendulum. Each complete movement back and forward is called a cycle. Cycles per second is called frequency. The more cycles per second means higher frequency. Using this kind of measurement it is possible to show that both vowels and consonants have their own distinctive resonance.
3. Auditory Phonetics
The branch of phonetics dealing with the physiological processes involved in the reception of speech. In simple terms what happens is that the outer ear collects the sounds from the world around us, the middle ear amplifies them and passes them to the inner ear where the impulses are relayed to the auditory nerve, a kind of fibre optic cable, and onwards to the speech centers in the brain. At various stages the sounds are processed into linguistic units and ultimately into items of meaning.
The areas of the brain considered to be the most important in the processing of language are Wernicke’s area (named after Carl Wernicke, 1848-1905, a German neurologist and psychiatrist) and Broca’s area (named after Pierre Paul Broca, 1824-1880, a French physician, surgeon, anatomist, and anthropologist). Both areas are normally located in the left hemisphere in right-handed people.
Not surprisingly auditory phonetics has become increasingly important to those linguists interested in the mental processes of language acquisition.
