112 



THE STUDY OF SPEECH CURVES. 



to the cavity. When the puffs are far enough apart, the vibration will 

 consist of a series of groups with decreasing ampUtudes, and the vibration 

 within a group will be independent of the interval at which the puffs come. 



This theory was made the 

 basis of some experiments on 

 resonance. A siren (figure 100) 

 was devised to blow resonators 

 by series of puffs. The blast 

 tube was cut entirely across and 

 the two parts were mounted 



from 

 motor 



Fig. 101.— Blast tube for 

 puff siren. 



Fig. 100.— Puff siren with resonator. 



in a holder (figure 101) and packed with felt so that the disc would pass 

 tightly between the two parts. Such an arrangement was necessary in order 

 to obtain sufficient blast to arouse the resonators without being disturbed 



Fig. 102. — Ring frame for puff siren. 



Fio. 103.— Disc for puff siren. 



by the rushing noise of lost air. The inner opening of the blast tube 

 was made into a sUt in order to make the puffs of definite forms. The 

 tube was held by a ring frame (figure 102) arranged to take eight blasts, 

 the object being to provide for blowing several resonators at the same time 



