20 



THE STUDY OF SPEECH CURVES. 



The explanation of the results is simple. When the (approximately) 

 parallel rays fall on a flat surface they are reflected back as they came 

 (figure 14, A, B, c, d). When the surface is convexly curved, they will 

 be bent outward from the center (figure 14, a', b', c', d')- From the move- 

 ments of the points upon the screen it is possible to deduce the curve 

 of the diaphragm. It is readily seen that the curve with vaseline fixation 

 must be of the general form indicated by figure 15, while that for metal 

 fixation must be of;ithe form shown in figure 16. 



Fig. 15. — Curve of bending for vase- 

 line fixation. 



Fio. 16. — Curve of bending for metal 

 fixation. 



Fig. 17. — Ideal of a sound box. 



Fig. 14. — Method of obtaining curvature of diaphragm 

 from the reflection of parallel rays. 



In a further series of experiments a micrometer screw was pressed 

 against the center of the diaphragm. In this way the relation could be 

 established between the degree of movement at the center and the bending 

 at each point of the diameter. It was my intention to investigate in this 

 way the relation between the deviation at the center and the movements 

 of the dots. The curve of bending for each degree of movement at the 

 center could thus be established. As the first results were in the main 

 the same as before, no quantitative work was done, although a completed 



