SEC. 2. SPEECH. 



915. All sounds as we have seen ( 840) 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 vibrations 

 of the glottis may however vary as to the degree of their regu- 

 larity ; 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 

 chamber, 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 whistling, 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. 



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

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



