GENERAL PAPERS 49 



erate voice can be heard and understood by auditors in the 

 most distant seats. According to experts, the music of the 

 pipe organ is satisfactorily rendered. The room is suited also 

 for orchestra music, although for this case the carpet is re- 

 moved from the stage so as to provide a sounding board for 

 the instruments. The reverberation is not excessive even 

 when no audience is present, so that rehearsals may be con- 

 ducted under favorable conditions. Several instances of 

 echoes have been reported, but these do not appear to prevent 

 the words of the speaker being understood. 



While the best evidence for the improved conditions was 

 furnished by the favorable opinion of the auditors, it was 

 thought desirable to get additional information by experiment. 

 Accordingly, the time of reverberation was determined ex- 

 perimentally and was found to be satisfactorily reduced from 

 what it had been before the correction was made. Echoes 

 were tested by the arc light reflector, and by a special arrange- 

 ment of megaphones. The padded walls diminished the sound 

 to such an extent that they produced little trouble, but several 

 unpadded walls of comparatively small area produced echoes 

 under particular conditions. For instance, when the speaker 

 faces such a wall so that the auditor can see the profile of his 

 face, an echo is perceptible. This is because the sound coming 

 directly to the auditor is diminished while that reflected from 

 the wall is augmented. 



The main conclusions of the investigation are as follows : 

 A room with large volume and hard, nonporous walls with but 

 little sound-absorbing materials will have a reverberation. If 

 the dimensions of the room are great, echoes are likely to be 

 set up, especially if the reflecting walls are curved. Walls re- 

 sponsible for the production of echoes may be located by using 

 an arc light backed by a reflector as a source of sound. Such 

 a room may have its faulty acoustics corrected by installing 

 sound-absorbing material, but this should be placed so as to 

 eliminate echoes as well as to reduce the reverberation. 



