74 
Proceedings of Royal Society of Edinburgh. [sess. 
of the mouth, as arranged for the giving forth of a vowel, was 
tuned as a resonator for a tone of a certain pitch, and that different 
pitches corresponded to the forms of the cavity for the different 
vowels. This he discovered not by the use of tuning-forks, hut 
by the peculiar noise produced in the mouth when the different 
vowels are whispered. The cavity of the mouth is then blown 
like an organ pipe, and by its resonance reinforces the correspond- 
ing partials in the rushing wind-like noise. The question was 
then taken up by Helmholtz, * and was treated in his usual 
masterly fashion. To determine the pitch of the cavity of the 
mouth, considered as a resonance cavity, he struck tuning-forks of 
different pitches, and held them before the opening of the mouth, 
widely opened. Then the louder the proper tone of the fork 
was heard, the nearer “it corresponded with one of the proper 
tones of the included mass of air.” As the shape of the mouth 
could he altered at pleasure, according to the vowel to he emitted, 
it was easy to discover the pitch of the included mass of air for 
each vowel. He came to the conclusion that “ the pitch of the 
strongest resonance of the oral cavity depends solely upon the 
vowel for pronouncing which the mouth has been arranged.” He 
also found the same resonances for men as for women and children. 
He then carefully examined the form of the oral cavity for each 
vowel, and showed how very slight changes would account for the 
quality being somewhat altered for different dialects. 
Helmholtz also showed that the tones of the human voice have 
peculiar relation to the human ear. Thus the upper partials of i 
are in the neighbourhood of e"" up to g"", and the human ear 
itself is tuned to one of these pitches, that is to say, by its 
resonance it favours the perception of these tones. Powerful male 
voices produce these partials strongly. Thus, a bass voice singing 
e' produced the 7 th partial d"", 8 th e"", 9 th f"", and the 10 th 
g"". Some of these partials, such as e"" and f"", may clash, 
and, by producing dissonance, give harshness to the voice. This 
* Helmholtz , ie TJeber die VoJcale ,” Archiv.f. d. holldnd. Beitrdge z. Natur. 
v.Heilkunde, Bd. i. pp. 354-355,1857; also “ Ueber die Klangfarbe der Vocale,” 
Gel. Ang. d. Tc. bayr. akad. d. Wissensch ., 1859, pp. 537-531 ; Poggendorffs 
Ann., Bd. 108, p, 180 ; also in Wissenschaftl. Abhandlungen , Bd. I. pp. 395, 
397 ; also Sensations of Tone , chap. v. p. 153. 
