438 KENNELLY AND AFFEL. 



phone-receiver terminals. With the diaphragm unloaded, the natural 

 angular frequency was found to be coo = 5645 rad/sec. and the damping 

 constant A = 211 per second. 



A small brass cylindrical mass of 0.98 gm. was then fastened, by 

 shellac, to the center of the diaphragm. Its diameter was approxi- 

 mately 3 mm., and its height about 6 mm. The diaphragm thus 

 loaded, was found to have a natural angular frequency of woi = 3980 

 rad/sec. with a damping constant Ai = 132 per second. 



Combining these two sets of observations, as in equations (4) and 

 (19), we obtain, as the equivalent mass of the unloaded diaphragm, 



m=^^^ = 0M8 gm. (5) 



Again, from (1) s = wq- m = 30.86 X 10« dynes/cm. (6) 



or by . (4) 5 = coor {m + my) = 30.86 X 10« " " (7) 



Similarly, from (2) r = 2m A = 409 dynes/kine (8) 



and (4) n = 2 (m + wi) Ai = 514 " " (9) 



The increase in the mechanical resistance of the loaded diaphragm 

 may be accounted for either by increase in air resistance of the load, 

 or in internal friction. 

 Finally from 



(3) A = VZ^ = 6.114 X W /^""^^ (10) 



absanipere 



Ai = ^IZ^i = V103.2 X 109 X 514 



= 7.283 X 10« , ^^"^^ (11) 



absampere 



The results of adding this load, and also two other successive loads, 

 to the center of the diaphragm, are given in Table III. Here Column 

 II gives the mass of the load in grams. Column III gives the measured 

 angular velocity coo of resonance, as obtained from the circle diagram 

 in each case. It will be observed that with the heaviest load, the 

 angular velocity was reduced nearly to one half of the initial angular 

 velocity, unloaded. Column IV gives the motional-circle diameters 

 in absohms. It will be seen that adding load to the diaphragm, first 

 increased, and then reduced the dimensions of the motional-impedance 

 circle. Column V records the depression angle of the diameter of the 

 motional-impedance circle in each case. Column VI gives the damp- 



