354 



DR. KCENIG S RESEARCHES ON 



from wliicli wind issues, the maximum displacement of air will result 

 when the slit is least covered, or when the point of greatest depression 

 of the curve crosses the front of the slit. The negative ordinates of the 

 curve correspond therefore approximately to condensations. Air is 



Fig. 7. 



now being supplied to the slits ; and when I open one or other of 

 the valves which control the air passages, you hear one or other of the 

 sounds. It must be audible to everyone present that the sound is 

 louder and more forcible with a difference of phase of ^ than in any 

 other case, that produced with f difference being gentle and soft in tone, 

 whilst the curves of phase and ^ yield tones of intermediate quality. 

 Dr. Kcenig found that if he merely combined together in various phases 

 a note and its octave (which was indeed the instance examined by nie 

 binaurally in 1876), the loudest resultant sound is given when the phase 

 difference of the combination is ^, and the mildest when it is f . 



Returning to Pig. G, in the second line are shown the curves which 

 result from the superposition of the odd members only of a harmonic 

 series of decreasing amplitude. On comparing together the curves of 

 the four separate phases, it is seen that the form is identical for phases 

 and ^, which show rounded waves, whilst for phases ^ and f the forms 

 are also identical, but with sharply angular outline. These two varie- 

 ties of curve are set out on the two edges of the highest metallic cir- 

 cumference in the apparatus depicted in Fig. 7. The angular waves are 

 lound to yield a louder and more strident tone than the rounded waves, 

 though, according to von Helmholtz, their tones should be alike. 



A much more elaborate form of compound wave siren was constructed 

 by Dr. Kcenig for the synthetic study of these phase relations. Upon 

 a single axis, one behihd the other, is mounted a series of 16 brass diskSj 



