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The acoustic aspect of speech sounds.






Any sound in nature is an acoustic phenomenon. It is a form of moving matter and energy. A sound is generated by a physical body which is set into vibration by some external force. When an external force is applied to a physical body the physical body begins to oscillate – to move forward and back. These alternate movements of the physical body produce condensations and rarefactions of air which are known as sound waves.

A speech sound is also a physical phenomenon. As it has been said before it is a product of the complex work of the speech mechanisms which regulate the air stream, thus producing condensations and rarefactions of air.

A sound has a number of physical properties: frequency, intensity, duration.

Frequency is a number of vibrations per second. A man’s ear may perceive the vibrations of the air when they occur at a rate of 16 to 20000 cycles per second. Frequency is measured in cycles per second.

Sound waves may rhythmical and non-rhythmical. When the vibrations are repeated at regular intervals of time we get rhythmical waves. They are perceived as vowels. When the vibrations are repeated as irregular intervals of time we get non-rhythmical waves. They are perceived as consonants.

Frequency of sounds depends upon the mass, length and tension of the vibrator. For example, the vocal cords which are greater in mass produce slow vibrations; they are perceived as low-pitched. If the vocal c-s are longer they produce slow vibrations too, which are also perceived as low-pitched. If the vocal c-s are less tense they produce slow vibrations which are perceived as low-pitched too, and vice versa.

That is why a man’s voice is usually lower than that of a woman. A child’s voice is usually the highest. Our perception of frequency is the pitch of the sound.

The second physical property of a sound is its intensity.

Intensity of a sound depends upon the force which is applied to a physical body. The greater the force, the larger the amplitude and vice versa. These sound waves have the same frequency, but the amplitude of vibration is different. The first has twice the amplitude of the second. It means that the sound of larger amplitude is louder, and the sound of smaller amplitude is less loud.

Changes in intensity are perceived as variations in the loudness of a sound. This is measured in decibels.

The third physical property of a sound is its duration. Sounds can only exist in time. The duration of a sound is measured in milliseconds - thousandths of a second. In speech there are no definite boundaries between different speech sounds: one speech sound gradually fades into another. Duration of a sound is perceived by man as its length.

All the physical properties of a sound exist simultaneously. They may be singled out and separated from one another only for purposes of acoustic analysis.

Phonology is a branch of phonetics which studies the functional aspect of speech sounds. Phonology is based on the phoneme theory, which came into being in Russia. As has been said before its founder was the Russian scientist prof. Ivan Alexandrovitch Baudouin de Courtenay (1845 - 1929).

Baudouin de Courtenay tried to analyze phonemes according to their functions. He did it through studying phoneme alternations and trying to explain this phenomenon. But his theory was known only to a few linguists (as Baudouin de Courtenay wrote only in Russian and Polish).

It was only after 1928 when the first International Linguistic Congress took place that this phoneme theory became widly known and spread. It has been thoroughly analysed and developed ever since.

Many followers continued the work of I. A. Baudouin de Courtenay, such as N. S. trubetskoy, some linguists of the Moscow school: R. I. Reformatsky, P. S. Kuznetsov and others. The most gifted pupil of Baudouin de Courtenay was prof. L. V. Shcherba (1880 - 1944).

Prof. Shcherba said that “… in actual speech we utter a much greater variety of sounds than we are aware of; in every language these sounds are united in a comparatively small number of sound types which are capable of distinguishing the meaning and the form of words; that is they serve the purpose of social intercourse. It is these sound types that we have in mind when discussing speech sounds. Such sound types are to be called phonemes. The various sounds that we actually utter and which are the individual representing the universal (the phonemes), are to be called phonemic variants.”

There are several conceptions of the phoneme both in our country and abroad. But linguists have not yet arrived at a definition of the phoneme acceptable to all.

Prof. V. A. Vassilyev developed L. V. Shcherba’s theory in his book “English Phonetics. A theretical course”. Here is his working definition of the phoneme to which we will stick: “The segmental phoneme is the smallest language unti that exists in the speech of all the members of a given language community as such speech sounds which are capable of distinguishing one word form from another word of the same language or one grammatical form of a word from another grammatical form of the same word.

The number of phonemes in each language is much smaller than the its number of allophones. It means that each phoneme has several allophones. Classification of allophones is very important for practical teaching because in actual speech it is allophones that people pronounce and not phonemes.

Allophones are divided into two groups: typical and subsidiary. The most representative allophone is called typical. It is the one that is not influenced by neighboring speech sounds. Typical allophones are described in English textbooks. They are included in the classification of the phonemes of the language. For example, the typical allophone of the /t/ phoneme is characterized by the following features: occlusive plosive, forelingual alveolar, voiceless- fortis, oral.

Subsidiary allophones may be positional and combinatory. Positional allophones are used in certain positions traditionally. For example, the English /l/ phoneme is always ‘dark’ in final position and before consonants as in ‘tell’, ‘ball’, ‘cold’, etc. the English /l/ phoneme is always ‘light’ in initial position as in ‘light’, ‘lesson’, ‘language’, etc.

Combinatory allophones are those which are influenced by the neighboring speech sounds. They are the result of assimilation, adaptation, accommodation, and of the specific process of sound transitions (VC, CV, CC, VV).


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