384 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



room at which the same phenomenon appeared, but generally in less 

 perfection."*^ 



Before undertaking the study of the complicated distribution of 

 sound intensity in a room with highly reflective walls, it was decided 

 to become better acquainted with the present experimental method by 

 an examination of a much simpler interference system ; namely, that 

 produced as nearly as may be by a single reflecting surface. This is 

 done in Experiment II following. Afterward, in Experiment III, it is 

 shown to be practicable to extend the investigation to a quantitative 

 determination of the distribution in a large auditorium. 



Experiment II. Stationary Wave Produced hy a Single Reflecting 

 Surface. — The arrangement of apparatus is shown in Figure 4. In 

 order to reduce the effects of reflection from the walls of the room, 



6.10 M 



Figure 4. — Position of apparatus in constant temperature room. 



they were curtained off with felt, F, 1.1 cm. thick, hung at a distance 

 of about 50 cm. from the walls. Felt of the same thickness was also 

 placed overhead, separated from the ceiling by about 50 cm. 



The organ-pipe, FJf 4, 705, serving as a source of sound, was placed 

 at P, near the center of the room. The telephone receiver, used in 

 Experiment I, was placed at T, about 70 cm. from the pipe. Leads 

 ran from the telephone to the condenser and transformer, which 

 together with the observer and galvanometer were in a distant 

 room. 



A reflecting surface of wood, 73 cm. wide hy 122 cm. high, was placed 

 vertically at W, and was mounted on a track so as to be capable of dis- 



3 Sabine, loc. cit. p. 8. 



