ABSOLUTE CALIBRATION OF CONDENSER TRANSMITTERS 105 



the two effects given above. The computations are based on as- 

 sumptions as to the transmitter contour which are quite removed from 

 the actual case. Thus for the first effect it has been suggested that the 

 transmitter may be replaced by an "equivalent" rigid sphere of equal 



Fig. 10.4- 



50 100 500 1,000 5,000 10,000 20,000 



FREQUENCY IN CYCLES PER SECOND 



-Pressure and field calibrations of No. 394-type condenser transmitter. 



20 50 100 500 1,000 5,000 10,000 20,000 



FREQUENCY IN CYCLES PER SECOND 



Fig. lOB — Field calibrations of No. 394-type condenser transmitter for normal and 



random incidence. 



volume ^2 or of equal diameter.^^ The data in Fig. 10^ are best fitted 

 by assuming a sphere of 9 cm. diameter, i.e., a diameter even larger 

 than that of the transmitter. For the second effect the assumption is 

 made that the face of the transmitter acts as an infinite wall, and that 



