Every act of speech presupposes the presence of a person who speaks and a person who listens. The speaker produces sounds, the sounds travel through the air to the listener in the form of complex combinations of sound waves, the listener hears and interprets them. Communication is possible only because the speaker and the listener interpret the sounds as units of the same language.
The articulatory (soundproduction) aspect. Speech sounds are products of human organs of speech. They result from the activities of the diaphragm, the lungs, the bronchi, the trachea, the larynx with the vocal cords in it, the pharynx, the mouth cavity with the speech organs situated in it and the nasal cavity. Sound production actually takes place in the larynx, the pharynx and the oral and nasal cavities. The air-stream coming from the lungs undergoes important modifications in them.
The acoustic aspect. Like any other sound of nature speech sounds exist in the form of sound waves and have the same physical properties – frequency, intensity, duration, and spectrum. Vowel sounds have at least two formants marked by F1 and F2, which are together responsible for the particular quality of each vowel type. F1 is characterized by lower frequencies, F2 by higher frequencies.
The auditory (soundperception) aspect. Speech sounds may also be analyzed from the point of view of perception. The perception of speech sounds involves the activity of our hearing mechanism, which can be viewed in two ways
Changes in intensity are perceived by our ear as variations in the loudness of a sound. The greater is the intensity of a sound, the louder is the sound. But our perception of loudness does not depend on intensity alone. A sound or a syllable may be perceived as louder, in comparison with neighboring sounds or syllables, because of a marked pitch change on it or because it is longer than the others. Moreover, some sounds, owing to their nature, are louder or more sonorous than others. Thus /a:/ is more powerful than /i:/, and vowels generally have more carrying power than consonants.
Our hearing mechanism acts as a monitor of what we ourselves are saying. The process of communication would be impossible if the speaker himself did not hear the sounds he pronounces. If the link between listening and pronouncing is disturbed, disturbances in the production of speech sounds are likely to appear. The better we hear the differences between the sounds, the better we pronounce them. Therefore in learning to pronounce the sounds of a foreign language one should bear in mind the importance of ear-training