36 



ILLINOIS STATE ACADEMY OF SCIENCE 



marked effect in improving the sound insulating proper- 

 ties for higher tones. Similar tests conducted upon a 

 number of window units of various types justify the 



105 



io« 



10' 



10- 



10' 



c, 



C4 



(612) 



Figure 6. 

 Curve 1. Reduction produced by single 

 glazed window 3/16" plate. Curve 2. 

 By double glazed window, with panes 

 set in putty. Curve 3. By double 

 glazed window, panes set in felt. 



statement that the sound-insulating properties of such 

 constructions depend upon the mass and stitfness of the 

 entire unit rather than upon the properties of the mater- 

 ials used. 



Figure 7 presents the reduction of sound intensity pro- 

 duced by doors of various types. Curve 1 is for a light 



Figure 7. 

 Curve 1. Reduction produced by door 

 of 1/4" steel. Curve 2. By %" plate 

 glass with cross bracing. Curve 3. 

 By 1/4" plate without cross bracing. 

 Curve 4. By -3/16" small leaded 

 panes. Curve 5. By %" panes 10" x 

 19". 



