The Anatomo-mechanical Aspect of Sound Production

II. THE ARTICULATORY CHARACTERISTIC OF THE ENGLISH SPEECH SOUNDS

Speech is impossible without the speech mechanism. So now our attention will be focused on the articulatory aspect of speech sounds.

Speech sounds are acoustic effects of the articulatory movements and positions of the human speech organs. The immediate source of speech sounds is the human speech mechanism developed and perfected in the process of the historical development of man. The organs of speech are the object of linguistic investigation mainly from the point of view of the functions they perform in speech production. So before analysing the linguistic function of phonetic units we need to know how the speech mechanism acts in producing oral speech.

According to their main sound-producing functions the speech organs can be roughly divided into the following four groups: the power mechanism (lungs, diaphragm, windpipe, bronchi), the vibrator mechanism (larynx, vocal cords, glottis), the resonator mechanism (nasal and mouth cavities) and the obstructer mechanism (tongue, lips, hard and soft palate, teeth).

From the lungs through the wind-pipe the air-stream passes to the larynx, containing the vocal cords. The opening between the vocal cords, through which the air passes, is called the glottis. The linguistic function of the vocal cords consists in providing the source of energy necessary for speech production. When the vocal cords are kept wide apart (i.e. the glottis is open) the air passes between the cords and the result is non-phonic breath. Then the vocal cords may be drawn together tightly, so that air cannot pass between them. The sudden opening of the glottis produces an explosion resembling a short cough; this sound is called the glottal stop. It often occurs in English when it reinforces or even replaces the sounds [p], [t], [k] or even when it precedes the energetic articulation of vowel sounds.

The most important role of the vocal cords is their participation in the production of voice. The effect of voice is achieved when the vocal cords are brought loosely together, creating an obstacle to the air stream; when the air pressure becomes very strong the air forces its way between the vocal cords thus making the, vibrate. When, as is usual, these vibrations are regular, they produce vocal tone, or voice, whose pitch depends on the frequency of vibrations. We are able to vary the speed of vibration of our vocal cords and thus to change the pitch. Conscious variations of pitch are responsible for intonation. We are also able to modify the size of the puff of the air which escapes at each vibration, thus changing the amplitude of the vibration, which corresponds to the loudness of the sound heard by a listener.

The air-stream, having passed through the vocal cords, is now subject to further modification, according to the shape of the pharynx, mouth and nasal cavities.

The direction in which the air-stream will follow from the pharynx depends on the position of the soft palate. When it is lowered, the pharynx opens into the nasal cavity. When it is risen, the air-stream comes to the mouth cavity. As in the mouth cavity a lot of movable speech organs are situated it can easily change its shape, thus forming the majority of speech sounds.

The movable (or active) speech organs, situated in the mouth cavity are: the tongue, the soft palate with the uvula, the lips and the lower jaw. Of all the movable organs within the mouth cavity the tongue is the most flexible and active. For convenience, the surface of the tongue or divided into several parts: the most flexible part of the tongue, which normally lies opposite the teeth ridge, is called the blade, the tip of the tongue being its extreme point. The part of the tongue next to the blade is called the front of the tongue. Then come the back and the root of the tongue.

The tongue being the most active speech organ in the mouth cavity, the main principles of the majority of articulatory classifications of vowels are based on the movements and positions of the tongue.

Дата добавления: 2014-01-04