SEC. 2. SPEECH. 



678. All sounds as we have seen ( 619) may be divided 

 into musical sounds, in which the vibrations are regular, and 

 noises, in which the vibrations are irregular ; but we have also 

 seen that the distinction between the two is not a sharp one. 

 The vibrations into which the air in the larynx is thrown by the 

 vibrations of the vocal cords in ordinary voice are on the whole 

 regular ; the sound so produced is a musical sound. The vibra- 

 tions of the glottis may however ^ary as to the degree of their 

 regularity ; and under certain circumstances they may be so 

 irregular that the sound becomes an undeniable noise; as for 

 instance in the sound which we call a ' cry ' or a ' shriek.' 



The sounds produced in the larynx like other musical sounds 

 consist of partial tones added to a fundamental tone, and are in 

 many cases very rich in partial tones. By modifying the shape 

 of the passage leading through the pharyngeal, the buccal, and 

 to a certain extent the nasal cavities, to the opening of the 

 mouth, which we have spoken of as a resonance tube or cham- 

 ber, and which, for reasons which we shall see, we may now call 

 the vowel chamber, we are able to render loud and prominent one 

 or other of the partial tones of a sound which is produced by 

 the larynx and thus to affect its quality as it leaves the mouth. 



We are also able, quite independently of the larynx (and 

 indeed independently of breathing), to create sounds by means 

 of parts of the mouth or other portions of the vowel chamber. 

 These are for the most part noises but, as for instance in whis- 

 tling, may be musical sounds. 



In speech we make use on the one hand of laryngeal sounds, 

 more or less modified in quality by the vowel chamber, and on 

 the other hand of sounds generated in various parts of that 

 chamber; our speech in fact consists of a basis of musical sounds 

 with an addition of noises. 



679. One great feature of speech is that it is " articulate ; " 

 it consists of syllables jointed together, the parts of speech which 

 we call words being formed of two or more syllables, or at times 

 of one only. In the great majority of syllables we recognize two 

 kinds of sounds which we call vowels and consonants. Though it 



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