300 ILLINOIS STATE ACADEMY OF SCIENCE 



masonry would be quite effective in stopping sound, pro- 

 vided the air space were not bridged over by solid material. 

 But the practical requirement of rigidity does not allow 

 the interposition of an unbridged air space, so that the 

 next best arrangement is used, namely, hairfelt or some 

 other air filled material as part of a floating floor, double 

 wall, etc. The problem is not yet solved in a practical 

 way for all conditions ; but progress has been made. 



For instance, in the Smith Music Building already men- 

 tioned, an effort was made by the Supervising Architect 

 and the writer to sound proof the entire building from at- 

 tic to basement. This problem involved the sound insula- 

 tion of some fifty small practice rooms, twelve studios, and 

 the larger concert hall, besides the acoustic control of 

 sounds of motors, fans and elevators. Double walls, floors, 

 and ceilings were constructed in accordance with the de- 

 scriptions set forth in the previous paragraph. Tight fit- 

 ting doors and windows were specified to prevent leakage 

 of sound and separate ventilation ducts were designed to 

 convey air to and from each room. 



Without dwelling on all the details it is perhaps suffi- 

 cient to state that some degree of success attended the ef- 

 forts. Students use adjacent rooms for piano practice, 

 singing, violin and other instrumental drill, etc., without 

 serious disturbance to each other. The rooms are not ab- 

 solutely sound proof nor does this appear necessary be- 

 cause the sound that leaks into the room is so diminished 

 in intensity that it is unnoticed when practice is in pro- 

 gress. The ventilators transmit sound between different 

 parts of the building, but the use of separate pipes for each 

 room diminishes the intensity of these transmitted sounds 

 so that they become unimportant compared with sounds 

 generated in the room itself. 



After several months of use, the building is considered 

 satisfactory for the purpose. Absolute sound proofing can- 

 not be attained without very unusual, and perhaps in- 

 practical, building constructions. It appears from the ex- 

 perience with the Music Building thus far that absolute 

 sound proofing is not essential. There are many things 



