VIBRATING TELEPHONE DIAPHRAGMS. 



421 



857^--' to 1,050'--', then adjusting the frequency to the particular 

 value (1,013'—') at which the Lissajous figure becomes a straight 

 line, measuring the motional impedance in the circle at this point, 

 and then deducing ^2° and (3^° geometrically. In the case of Fig. 4, 

 ^81*^ = 36° 38' and I3J^ = 46° 20'. The precision obtained in measur- 

 ing these angles corresponds however to a probable error of one 

 degree for a single observation, so that reliance cannot be placed on 

 the minutes of arc. 



The following table collects the results obtained with one bipolar 

 telephone^ receiver B with two successive diaphragms, i. e., dia- 



TABLE I. 



Effect of Diminishing Resonant Frequency on Pi° and ^j°. 



Note: In the case of Test 2, the load of 0.6 gm. was applied to the dia- 

 phragm at its center ; whereas in the case of Test 3 it v/as applied at a point 

 I cm. off the center. 



phragm B and diaphragm i. The first line in the table corresponds 

 to the set of observations given in Fig. 4, where there was no load 

 attached to the center of the diaphragm, the diameter Zm of the 

 motional-impedance circle was 81.25 ohms, the resonant frequency 

 /o was 958 '-', the damping coefficient A, 245 hyperbolic radians per 

 second, the force constant A, 5.49 megadynes per absampere, the 

 equivalent mass m, 0.757 gm., the frictional or mechanical resist- 

 ance r, 371 dynes per kine, the elastic constant s, 25.75 megadynes 

 per cm. At the frequency f, of 1,013 '— ', the angle /So" was 46° 20', 

 and at 958 ^, /3i° was inferred to be 36° 38'. 



The successive series of observations 2, 4, and 5 were obtained 

 by attaching increasing loads to the diaphragm, so as to lower the 



' The details of this receiver are given In the paper of bibliography No. 10. 



