2. PHONETICS

1 2. PHONETICS 2.1 Scope of phonetics PHONETICS is the science which studies the characteristics of human sound-making, especially those sounds used in speech, and provides methods for their description, classification and transcription.

SPEECH SOUNDS may be studied from different angles, three branches of phonetics, articulatory phonetics, auditory phonetics and acoustic phonetics.

2.1.1 Articulatory phonetics Speech sounds may be studied from the point of view of the speaker, that is, we may examine the way in which a speech sound is produced to discover which vocal organs are involved and how they coordinate in the process. This aspect of phonetics is called ARTICULATORY PHONETICS.

2.1.2 Auditory phonetics A meaningful act of speech has another end – the reception end. The sounds produced by the speaker will be received by the hearer. Speech sounds therefore may also be studied from the hearer‘s point of view. We may look into the impression a speech sound makes on the hearer as mediated by the ear, the auditory nerve and the brain. This area of research is known as AUDITORY PHONETICS.

2.1.3 Acoustic phonetics To make a speech sound visible so that we can measure its components objectively we must then go into the domain of ACOUSTIC PHONETICS, which studies the physical properties of speech sounds, as transmitted between mouth and ear. Instruments, such as the oscillograph and the sound spectrograph, have been used to translate a sound into a visual representation of its components in terms of frequency and intensity. The sound spectrograph will, in addition, show the formants of vowels.

2.2 The Vocal Organs The vocal organs (see Fig. 1), or the speech organs, are organs of the human body whose secondary use is in the production of speech sounds. The vocal organs may be viewed as consisting of three parts, the initiator of the air-stream, the producer of voice and the resonating cavities. 2

2.2.1 The initiator of the air-stream The first requisite for the production of a speech sound is that there is an air-stream.

2.2.2 The vocal cords The air-stream provided by the lungs has to undergo a nuntoer of modifications to acquire the quality of a speech sound. The first point where it is possible to modify the air-stream is at the top of the windpipe, which ends in a bony structure called the LARYNX.

Inside the larynx are the VOCAL CORDS. They are in fact two folds of membrane (hence also the name vocal folds), which are fixed together at the front but horizontally moveable at the back.

The space between the vocal cords is termed the GLOTTIS. In speech the vocal cords have three main functions. (1) The vocal cords may be closed tightly so that the airstream from the lungs is blocked and the air pressure behind them builds up. This phenomenon is called the GLOTTAL STOP and symbolized as[?]. Thus the sound is inaudible, but it has its effect on surrounding segments.

In English, it often occurs initially to pronounce a word like ‗idiot‘ which begins with a vowel.

(2) If the vocal cords are brought together to the extent that there is only a narrow passage between them, the pressure of the airstream will set them in vibration.

The result is a sound. The sound has a regular waveform and the number of vibrations in a second is fixed, so that we can perceive its pitch. In phonetics, this sound is called VOICE, and sounds produced while the vocal cords are vibrating are called VOICED SOUNDS. Consonants like English [b,m,z] are voiced. Vowels are usually voiced, too. 3

The PITCH of a sound depends on the rate of vibration of the vocal cords, which in turn is determined by the length of the vocal cords.

When the vocal cords are not vibrating at the time of its production, the resultant sound is called a VOICELESS SOUND. Consonants like [f, s, p] are voiceless sounds.

2.2.3 The resonating cavities In the human speech mechanism, there are three resonating cavities: the PHARYNS, the NASAL CAVITY and the ORAL CAVITY.

2.2.3.1 The pharynx The PHARYNX stretches from the top of the larynx up to the back of the nasal cavity and serves as the container of a voiume of air which can be set into vibration in harmony with vibrations coming from the vocal cords.

2.2.3.2 The nasal cavity The NASAL CAVITY is of fixed dimensions and shape, and its contribution to speech is entirely a matter of resonance.

2.2.3.3 The oral cavity The ORAL CAVITY is by far the most important of the three cavities; it is here that most of the distinctions of articulate speech are fashioned.