Acoustic aspect of speech sounds

Speech sounds can be analysed from the viewpoint of three as­pects: (1) acoustic, (2) physiological and articulatory, (3) functional.

Phonetics is connected with linguistic and non-linguistic sciences: acoustics, physiology, psychology, etc. Speech sounds have a number of physical properties, the first of them is frequency, i.e. the number of vibrations per second.

The vocal cords vibrate along the whole of their length, producing fundamental frequency, and along the varying portions of their length, producing overtones, or harmonics. When the vibrations pro­duced by the vocal cords are regular they produce the acoustic impression of voice or 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.

The complex range of frequencies which make up the quality of a sound is known as the acoustic spectrum.

The second physical property of sound is 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; the greater the pressure on the ear-drums, the louder the sound. Intensity is measured in decibels (dbs).

Although acoustic descriptions, definitions and classifications of speech sounds are considered to be more precise than articulatory ones, they are practically inapplicable in language teaching, because the acoustic features of speech sounds cannot be seen directly or felt by the language learner. Acoustic descriptions, however, can be ap­plied in the fields of technical acoustics. They are also of great theo­retical value.

The research work made in acoustic phonetics is connected with 1) the methods of speech synthesis and perceptual

experiment for the study of cues of phonemic distinctions and for the exploration of dif­ferences in tone and stress; 2) the design of speech recognizing ma­chines, the teaching of languages, the diagnosis and treatment of patho­logical conditions involving speech and language.

The future work in acoustic phonetics will be connected with brain functioning and ar­tificial intelligence. “Experimentation will involve the whole of speech programming and processing, including the relations between the acoustic level of speech and operations at the grammatical, syn­tactical, lexical and phonological levels.”

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