192 Proceedings of Indiana Academy of Science 



of the main portion of a reflected sound wave. For this portion of 

 wave the law that the angle of incidence equals the angle of reflection 

 is as true as it is in the case of light. The writer has proved this state- 

 ment in the case of sound pulses from electric sparks, by photographing- 

 such waves in various stages of reflection from surfaces of several dif- 

 ferent shapes. 



Let us apply the law to the case of a plane sound wave entering 

 the large end of a flared horn, as in figure 1. The portion of the wave 

 which is lettered A is reflected back and out at the end it entered, after 

 but a single reflection. The portion lettered B backs out after two 

 reflections, while C does so after six reflections. Reference to the photo- 

 graphs published in the author's papers referred to above, shows clearly 

 and conclusively that this is exactly what happens. The data therein 



l*"i>;. 2. Cross section of a multiplo' conical horn, showinj^ how wave energy may 

 be reflected to the small end of the horn, resulting in incieased amplification. 



published shows that a horn of wide angle "condenses" very little more 

 energy than one of small angle. 



Suppose now that we take an ordinaiy conical horn H, shown in 

 cross section in figure 2, and place within it and coaxial with it a sim- 

 ilar but smaller horn S. Then the portion of a sound wave A, instead 

 of backing out of the horn after one or two reflections, is reflected 

 first from the inner surface of the outer horn H, then from the outer 

 surface of the inner horn S, then again from the inner surface of H, 

 thence to the small end of the horn. Likewise, the portion of the wave 

 lettered B, and therefore all portions of the wave between A and B. 



To take care of the energy falling on the inner surface of the horn 

 S, a third and still smaller horn may be placed within S, and so on. 

 Thus, by using a number of nested, and spaced horns the energy con- 

 densed at the small end is materially increased over anything possible 

 with a single horn. 



