PAPERS PRESENTED AT GENERAL SESSIONS 



35 



The lowest cui^'e shows the reduction produced by a win- 

 dow with panes 3/16 of an inch thick, composed of two 

 thin sheets of glass with an intervening sheet of celluloid. 

 Curve 2 is for a similar window with panes of solid plate 

 glass of the same thickness. The effect of the greater 

 stitfness of the solid glass pane in producing a greater 

 reduction in the intensity of the transmitted sound is 

 shown. Curve 3 is for an identical window using plate 

 glass 1/4 of an inch thick. Translating the logarithmic re- 

 ductions into numerical ratios, the curves for the heav- 

 iest window show a reduction in the ratio of 100 to 1 at 

 middle C and a reduction of about 500 to 1 for tones in 



105 



10* 



10^ 



102 



10' 



3 



2 

 1 



C2 



C3 



C4 



512) 



c, 



Figure 5. 

 Curve 1. Reduction produced by triplex 

 glass. Curve 2. By 3^6" plate. 

 Curve 3. By M" plate. 



the second octave above middle C. In Figure 6, is sho"vvn 

 the relative transmissions of sound by a single and a 

 double pane window. The lower cuiwe gives the reduc- 

 tion produced by a window of lighter glass than those 

 shown in Figure 5. Curve 2 is for a double glass window, 

 the panes being set in putty upon opposite sides of the 

 sash, with an inter^'ening air space of 134 inches. The 

 third curve is for the same window, the panes being set in 

 felt rather than in putty. As is shown, the merit of the 

 double glazed over the single glazed construction is 

 slight for the lower tones, but the former produces a 

 somewhat higher reduction for the upper tones. Similar- 

 ly, the effect of the felt in reducing the transmitted sound 

 is negligible for the lower tones, but does produce a 



