450 



KENNELLY AND AFFEL. 



TABLE V {Continued). 



The second part of the Table gives the results obtained from the 

 motional-impedance circle, and from the amplitude measurer. The 

 circle diagram for the case of receiver b, is given in Figure 14. The 

 outer circle is the motional-impedance circle, plotted to a scale of 

 ohms, from observations with the Rayleigh bridge (Fig. 12). The 

 inner circle, is a circle of maximum cyclic vibration velocities, at the 

 center of the diaphragm, as deduced from vibration amplitudes ob- 

 served with the vibration explorer, plotted vectorially from the origin 

 O. It is shown in Appendix I (40) that the motional impedance, 

 when the sinusoidal testing current is maintained constant, becomes the 

 product of the vibrational velocity x and a constant. The inner circle, 

 thus conforming satisfactorily to the impedance circle, supplies a 

 check upon the theory of the case. Theoretically, the mean vibra- 

 tion amplitude should be measured over the air-gap, instead of at the 

 center of the diaphragm; but the difference is probably not material. 

 It will be noticed that the resonant frequency fo, on the diameter of the 

 impedance circle, is 1020.4 ■^^ , with a corresponding resonant angular 

 velocity wo, of 6412 radians per second. The frequencies at the 



