384 



PKO( EEDINQS «>F THE AMI. KM \N \< WU.MY. 



room ;tt which the same phenomenon appeared, but generally in less 

 perfection." 3 



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 maybe by a single reflecting surface. This i> 

 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 If. Stationary Wave Produced by a Singh 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, 



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



they were curtained off with felt, P, 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 . r >0 cm. 



The organ-pipe, F#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 7<> 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 Burfaceofwood, 7:5 cm. wide by L22 cm. high, was placed 



Ideally at W, and was mounted on a track so as to be capable ot'dis- 



3 Sabine, !<"•. lit. p. 8. 



