ARTICULATION TESTING METHODS 



827 



Syllable articulation "S" 97.5 per cent. Practically identical results 

 were obtained with the "Master Reference System" "^ with the system 

 set for optimum received speech level, i.e. a sensation level of 70 db, 

 average distance from lips to transmitter 1.5 inches. 



(6) Auxiliary Circuit of the Master Reference System. — The auxiliary 

 circuit of the master reference system consists of networks which are 



2 3456789 2 3 



100 1000 



FREQUENCY 

 Fig. 6 — Insertion loss of auxiliary networks 



5 6 7 89 



10,000 



I 



lb MILES 



VZA GAUGE 



CABLE 



I 



1.5 MILES 



#24 GAUGE 



CAPLE 



Fig. 7 — Carbon transmitter circuit 



inserted into the otherwise distortionless reference system, to give it 

 a frequency resonance around 1,100 cycles. The insertion loss of the 

 networks is shown in Fig. 6. This loss is approximately equal to the 

 combined losses of the No. 1 transmitter and receiver distortion 

 networks of the Master reference system. Sensation level 74 db 

 L = 89.2 per cent, S = 72 per cent. 



' L. J. Sivian, "A Telephone Transmission Reference System," Electrical Com- 

 munication, 3, Oct. 1924. M. Cohen, "Apparatus Standards of Telephonic Trans- 

 mission." W. H. Martin and C. H. G. Gray, "Master Reference System," 5p// 

 Tech. Jour., July, 1929. 



