VELOCITY MICROPHONES 



199 



The voltage output in abvolts is 



e = Blx 



9.51 



where B = flux density, in gausses, 



/ = length of the ribbon, in centimeters, and 

 X = velocity of the ribbon in centimeters, per second. 

 The response characteristic of a mass controlled ribbon located in a large 

 circular baffle. Fig. 9.17, computed from equation 9.51 is shown in Fig. 9.18. 



2 3456769 2 3456769 2 3456789 



.01 J I 10 



H 

 X 



Fig. 9.18. Computed open circuit voltage response frequency characteristic of a mass con- 

 trolled, electrodynamic ribbon located in a large circular baffle. 



The experimental response of a ribbon microphone with a circular baffle is 

 shown in Fig. 9.19. The agreement between the measured response and 

 the computed response is quite good. There is some deviation between 

 R/\ = .5 and R/\ = .8. There is also some discrepancy in this region be- 

 tween computed and measured pressures (Figs. 9.14 and 9.15). It is in- 

 teresting to note that the theoretical response of the pressure gradient 

 microphone and the ribbon in a baffle is practically the same. Figs. 9.11 

 and 9.18. 

 The measured directional characteristics of the ribbon microphone with 



