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BELL SYSTEM TECHNICAL JOURNAL 



projectors were carefully directed to cover uniformly the area around 

 the amphitheatre and were supplied with sufficient power so that 

 the speaker could be heard for at least a thousand feet from the out- 

 side of the amphitheatre. It was found, however, that while these 

 projectors are highly directive, some of the sound from them could 

 be heard inside the amphitheatre. This sound leakage at the western 

 side was particularly serious because of the fact that it reached the 

 rear seats inside of the amphitheatre sufficiently far enough ahead of 

 the corresponding sounds directly from the speaker to be noticeable. 









-* Large Projecto 

 ■* Small Projector 

 •I TelephoneTransm 



Fig. 11 — Arrangement of Projectors at Arlington Amphitheater 



To overcome this, the small projectors 29, 31, 32 and 34, placed on 

 top of the arch over the platform, were directed at the rear seats and 

 given sufficient volume output to overcome the sound reaching these 

 seats from the loud speakers on the colonnade. 



t The adjustment of the power to these small projectors required 

 great care because if given too great volume, bad reflections would 

 be set up in the amphitheatre. On the other hand if this volume were 

 not great enough, the outside projectors would cause serious inter- 

 ference. The small projectors 27 and 28 were used to overcome the 

 sound leakage effects on the top of the west side of the colonnade. 



