502 MOVEMENTS- VOICE AND SPEECH. 



cause of these differences was studied very closely in the latter part of the 

 last century, but it has lately been rendered clear by the researches of Helm- 

 holtz and of Koenig. In this connection it will be sufficient to indicate the' 

 results of the modern investigations very briefly. It will be seen in studying 

 the physics of sound in connection with the sense of hearing, that nearly all 

 sounds, even when produced by a single, vibrating body, are compound. Helm- 

 holtz, by means of his resonators, has succeeded in analyzing the apparently 

 simple sounds into different component parts, and he has shown that the qual- 

 ity of such sounds may be modified by re-enforcing certain of the overtones, as 

 they are called, such as the third, fifth or octave. For those who are famil- 

 iar with the physics of sound, the explanation of the mechanism of the pro- 

 duction of vowel-sounds will be readily comprehensible. The reader is re- 

 ferred, however, to the remarks upon overtones in another part of this work, 

 under the head of audition, for a more thorough exposition of this subject. 

 The different vowel-sounds may be emitted with the same pitch and intensity, 

 but the sound in each is different on account of variations in the resonant 

 cavities of the accessory vocal organs, especially the mouth. It has been ascer- 

 tained experimentally that the overtones in each instance are different, as they 

 are re-enforced by the vibrations of air in the accessory vocal organs, in some 

 instances the third, in others, the fifth etc., being increased in intensity. 

 This can hardly be better illustrated than by the following quotation from 

 Tyndall, in which modern researches have been applied to the vowel-sounds 

 of the English language : 



" For the production of the sound U (oo in hoop), I must push my lips 

 forward so as to make the cavity of the mouth as deep as possible, at the same 

 time making the orifice of the mouth small. This arrangement corresponds 

 to the deepest resonance of which the mouth is capable. The fundamental 

 tone of the vocal chords is here re-enforced, while the higher tones are thrown 

 into the shade. The U is rendered a little more perfect when a feeble third 

 tone is added to the fundamental. 



" The vowel is pronounced when the mouth is so far opened that the fun- 

 damental tone is accompanied by its strong higher octave. A very feeble 

 accompaniment of the third and fourth is advantageous, but not necessary. 



" The vowel A derives its character from the third tone, to strengthen 

 which by resonance the orifice of the mouth must be wider, and the volume 

 of air within it smaller than in the last instance. The second tone ought to 

 be added in moderate strength, whilst weak fourth and fifth tones may also 

 be included with advantage. 



" To produce E the fundamental tone must be weak, the second tone com- 

 paratively strong, the third very feeble, but the fourth, which is characteris- 

 tic of this vowel, must be intense. A moderate fifth tone may be added. 

 No essential change, however, occurs in the character of the sound when the 

 third and fifth tones are omitted. In order to exalt the higher tones which 

 characterize the vowel-sound E, the resonant cavity of the mouth must be 

 small. 



" In the production of the sound ah I the higher overtones come princi- 



