MECHANICS OF THE HUMAN VOICE 25 1 



have used — gelatine, water, etc. — have to be renewed every few days. 

 If they can be replaced by durable materials a vocal organ can be 

 built that will sing vowels at any pitch, giving true human tones 

 instead of the bleating tones of the present vox humana register. 

 An apparatus of this kind is now being constructed on funds from 

 another source ; if successful it can be added to the regular church 

 organs and used to sing the vowels during chants. 



On the basis of the principles just stated, namely, modification of 

 the cord vibrations by the adjustment of the cavities and softness of 

 the cavity walls, work on the curves has led to the following further 

 conclusions. 



The resonance tones of vowels have definite regions of pitch which 

 have definite relations to one another. For the effect on the ear 

 changes in the region of pitch may be compensated by changes in 

 the relation and by the introduction of new tones. Both Helmholtz 

 and Hermann are therefore correct in assuming in general definite 

 regions of tone for a particular vowel, but the tones can vary greatly 

 if only the necessary compensations are made to deceive the ear. 



It is to be noted that in their essentials the apparent contradiction 

 between the theories of Helmholtz and Hermann disappears. We 

 can, like Hermann, assert that the cavity tones are the independent 

 variables ; but when we add that the cavities modify the mode of 

 vibration of the vocal cords so as to bring out certain overtones from 

 the cord tone, we reach a result essentially in agreement with the 

 theory of Helmholtz. 



A great difficulty in studying the speech curves lay in assigning 

 any physical meaning to a single wave of the curve. The curves 

 did not permit any interpretations according to the usual views of 

 resonance of overtones ; otherwise mathematical analysis of Fourier 

 would have furnished immediate results, and harmonic analyzers, 

 like that of Michelson, would have made it possible to spare a great 

 amount of work. A mathematical treatment of vibrations on new 

 principles was out of my power, but a physical synthesis was 

 attempted. A machine was constructed to register the curves of 

 two superimposed vibrating springs of different dampings acted 

 upon by magnetic impulses of different degrees of suddenness. If 

 it can be made to furnish curves like those obtained from speech, 

 we shall have the following results : i . The principles of vibration 

 on which it acts can then be assumed to be the same as those of the 

 voice. 2. An atlas of curves can be prepared in such a way that 

 when a given speech curve is found to be like a specimen in the 



