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BELL SYSTEM TECHNICAL JOURNAL 



cubic feet, and a seating capacity of about 4000. A floor plan of the 

 auditorium showing the location of the loud speakers and of the 

 control equipment is given in Fig. 3. The loud speakers are placed so 

 that each of the three sets radiates into a solid angle including as nearly 



MEZZANINE 



G'' 



DIRECTORS BOX 

 WITH CONTROL 

 EQUIPMENT 



ORCHESTRA 



Fig. 3 — Floor plan of Constitution Hall, Washington, D. C, showing locations of 



loud speakers. 



as possible all the seats of the auditorium. Figure 4 shows the rever- 

 beration-frequency characteristics of Constitution Hall. The values 

 given by the curve for the empty hall were measured through the use 

 of the three regular loud speakers and several microphone positions in the 

 room. The values for the hall with an audience present were calcu- 

 lated from known absorption data for an audience, and the optimum 

 values are taken from accepted data for an auditorium of the volume 

 of this one.^ The reverberation times were considered satisfactory and 

 no attempt was made to change them for this demonstration. The 



