in PHONATION AND AKTICULATION 159 



partials, while others are excluded, according as it assumes the 

 position for saying or singing one or other of the vowels. 



The earliest experiments on the physical nature of vowel tones 

 were made by Willis (1829), and Wheatstone (1837), who con- 

 structed a theory of vowel tones which remained unnoticed for 

 twenty years. Bonders (1857) first showed clearly that the cavity 

 of the mouth for different vowels is tuned to different pitches. It 

 forms a resonator which can be tuned to the different sounds 

 characteristic of different vowels. 



In order to ascertain the tones which characterise the several 

 vowels, Bonders cut out the laryngeal sounds which usually 

 accompany them, by whispering them one after the other ; under 

 these conditions sounds are produced in which the ear can re- 

 cognise a definite pitch in the dominating tone, which varies for 

 the different vowels, but is approximately constant in all persons 

 of the same sex and age. These sounds are caused by the air-blast 

 in the oral cavity, where the tones are reinforced so that it is 

 possible to recognise the different vowels, although they are 

 weaker than the normal voice. In speaking or singing the 

 sounds given out by the resonator are associated with the laryngeal 

 sounds, and the specific partials of the different vowels are greatly 

 reinforced, and give the laryngeal sounds their characteristic 

 timbre. 



In his classical work Die Lelire von den Tonempfindungen 

 Helniholtz placed his theory of vowel-tones on a strict scientific 

 basis, and extended Bonders' hypothesis. According to Helmholtz 

 " the vowels of speech are in reality tones produced by membranous 

 tongues (the vocal cords) with a resonance chamber (the mouth) 

 capable of altering in length, width, and resonant pitch, and hence 

 capable also of reinforcing at different times different partials of 

 the compound tone to which it is applied." l 



In order to determine what partial tones of the mouth cavity 

 give their vowel character to the laryngeal tones Helmholtz 

 employed a more accurate method than that of Bonders. He 

 struck tuning-forks of different pitch, and held them before the 

 open mouth arranged for the pronunciation of each vowel in turn. 

 The pitch of the fork which then sounded loudest gave the proper 

 tone to which the mouth was tuned. Helmholtz found that the 

 pitch of the vowels rises progressively from u (oo) to a (ah) and 

 from a (ah) to i (ee). In u, o, a he only distinguished a single 

 note ; in a e , e, i, o e , u 1 two different notes, because the mouth cavity 

 is divided in the pronunciation of these vowels by the rise of the 

 tongue (Fig. 101). He maintained that the vowel notes are the 

 same in men, women, and children. The least change in the 

 position of the oral cavity modifies the quality of the tone, and 

 thus gives rise to the intermediate vowels which are so common 



1 Sensations of Tone, Helmholtz, tr. Ellis from 3rd ed., p. 153, 1875. 



