TELEPHONE DIAPHRAGMS. 



435 



The following Table gives the values of the elastic constant s of the 

 diaphragms, as determined from the force-deflection curves in Figure 

 9. It should be noted that the sample diaphragm "japanned" was in 



TABLE II. 

 Elastic Constants of Diaphragm from Static Deflection Measurements. 



each case a different sample from the diaphragm of the same thickness 

 numl)er "unjapanned." Consequently, it is not safe to assume that 

 the difference appearing in the Table between the values of s for a 

 japanned and unjapanned diaphragm of the same thickness number, 

 is due to the effect of japan. Such differences are more likely to be 

 due to accidental variations in the thickness or quality of the two 

 diaphragms. The japan coating had an average thickness of 0.075 

 mm. and does not seem to have appreciably affected the observed value 

 of s. Below the thickness of plate No. 34, however, (0.23 mm.) the 

 values of s, with the magnet in place, are markedly greater than with 

 the magnet removed. 



Judging from measurements of the effective value of s obtained by 

 other methods, its direct determination by static deflection is unre- 

 liable, except as a rough approximation, for the purpose of arriving 

 at the four essential constants of a telephone-receiver diaphragm, for 

 the following reasons: 



