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BELL SYSTEM TECHNICAL JOURNAL 



for engineering purposes, in that it measures directly the thing of 

 most interest, namely, the degrading effect upon telephone conversa- 

 tion of introducing electrical distortion into the transmission circuit. 

 However, the application of the results is not limited to this particular 

 field. 



Method of Measuring the Quality of Speech 



Briefly stated the method consists in pronouncing detached speech 

 sounds into the transmitting end of the system and having observers 

 write the sounds which they hear at the receiving end. The com- 

 parison of the called sounds with those observed shows the number 

 and kinds of errors which are made. The per cent of the total sounds 

 spoken which are correctly received is called the articulation of the 

 system. 



Table I. 



Classification of the Speech Sounds. 

 Pure Vowels 



Combinational and Transitional Vowels 

 w — y— ou — I — h 



