Acoustic aspect of speech sounds

The branch of phonetics that studies the linguistic function of consonant and vowel sounds, syllabic structure, word accent and prosodic features, such as pitch, stress and tempo is called phonology.

We consider the discriminatory function to be the main linguistic function of any phonetic unit we cannot ignore the other function of phonetic units, that is, their role in the formation of syllables, words, phrases and even texts.

At the faculties of foreign languages in this country two courses of phonetics are introduced:

Practical or normative phonetics that studies the substance, the material form of phonetic phenomena in relation to meaning.

Theoretical phonetics which is mainly concerned with the functioning of phonetic units in the language. Theoretical phonetics, as we introduce it here, regards phonetic phenomena synchronically without any special attention paid to the historical development of English.

Phonetics is itself divided into two major components: segmental phonetics, which is concerned with individual sounds (i.e. "segments" of speech) and suprasegmental phonetics whose domain is the larger units of connected speech: syllables, words, phrases and texts.

Using various apparata investigating the fundamental characteristics of human speech phoneticians work at the problem of the perception of human speech. Further step is to teach the machine to respond to human speech and to synthesize it. There is a possibility to identify people through their speech by means of vocal-decorders, to "read" the text from a printed page in a "synthetic" voice. Extensive collaboration of phonetics and sound engineering is leading to phonetic typewriters which will "listen" to human speech and print it.

The practical application of phonetics is great in medicine while correcting various deviations from normal human speech; it is also important to train teachers for deaf and dumb people.

Phonetics is taught to professional singers and actors to make them masters of their own voice, to enlarge its possibilities.

We can't imagine designing and improving systems of writing and spelling without phonetic foundation; working at the orthographies of unwritten languages, creating new alphabets is based on phonetical systems.

2. Aspects of a speech sound. Methods of investigation in phonetics & phonology

Speech sounds can be analysed from the viewpoint of three as­pects:

1. Acoustic,

2. Articulatory and physiological,

3. Functional (phonological),

4. Auditory.

Speech sounds have a number of physical properties:

1. Frequency – the number of vibrations per second.

When the vibrations pro­duced by the vocal cords are regular (periodical) they produce musical tone. When they are irregular noise is produced. When there is a combination of tone and noise, either noise or tone prevails. When tone prevails over noise sonorants are produced. When noise prevails over tone voiced consonants are produced.

Perception of the pitch of a speech sound depends upon the fre­quency of vibration of the vocal cords. The higher the pitch of vibra­tions, the higher the pitch level. The frequency of sound depends on certain physical properties of the vibrator, such as mass, length and tension

2. Intensity. Changes in intensity are perceived as variation in the loudness of a sound. The greater the amplitude of vibration, the greater the intensity of a sound. Intensity is measured in decibels (dbs).

3. Any sound has duration, it is its length or quantity of time during which the same vibratory motion, the same pattern of vibration, are; maintained. The duration of speech sounds is usually measured im milliseconds (msecs)

4. Composition or complexity – is closely connected with the frequency and intensity. The vocal cords do not only vibrate as a whole, but also in their parts. The sound produced by the vibration of the whole length of the vocal cords is called fundamental. Sounds produced by the vibrations of the parts of the vocal cords are called overtones or harmonics.

The analysis of a sound frequency and intensity at a definite period of time can be presented graphically with the help of a sound spectrograph. Acoustic characteristics of speech sounds are repre­sented by spectrograms:

1) linear (dynamic)

In linear representations of intensity spectrograms the strength of harmonics is adequate to the blackness of spots: the stronger the harmonic, the blacker is the spot.

2) instant (intensity).

In instant spectrograms intensity is represented by vertical dimen­sions, frequency–by horizontal dimension.

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