ARTICULATION TESTING METHODS 



839 



From these three sets of data and from other available data which 

 could be applied to this problem, the curve shown in Fig. 8 was 

 constructed. It gives the sound articulation which would be obtained 

 for a circuit such as the auxiliary circuit of the master reference 

 system, when the number of sounds that are spoken at a time, that 

 is, before the observer starts writing, is represented by the abscissa. 

 It is evident from the shape of this curve that the assumptions under- 

 lying the statistical formula? are valid for syllables having three or 

 less sounds per syllable, and that they will break down for the more 

 complex types of syllables. These assumptions might be expected 

 to break down also, for certain extreme types of distortion. 



Definite relations between the vowel, consonant, sound, and syllable 

 articulations for both the old and the new techniques, have been 

 derived by statistical theory. An experimental relationship between 

 these quantities is shown in Figs. 9 and 10. These were obtained by 

 an analysis of the errors of a large number of tests with widely different 

 types of distortion, the data in Fig. 9 being taken with the old and 

 the data in Fig. 10 with the new technique. 



In the figures observed values of sound articulation have been 

 plotted against the corresponding observed syllable articulation values. 

 The solid curves in the two cases were calculated from Equations 7 

 and 8, respectively. The observed values agree reasonably well with 

 the theoretical curves. 



There is very little correspondence between the vowel and syllable 

 or consonant and syllable articulation. The table below shows that 



TABLE XIII 

 Vowel, Consonant, and Syllable Articulations 



FC2 



3,750 L.P.F. 



750 H. P.P. 



2,850 L.P.F. 



1,000 H. P.P. 



89.8 

 90.4 



85.4 

 86.2 



a circuit which discriminates against the vowels may have a syllable 

 articulation equal to another circuit which discriminates against the 

 consonants. However, it is seen that the product VC- is equal to 5 

 as the statistical theory indicates. If then the sound, or vowel and 

 consonant articulations are knoivn, it is possible to calculate the sylluble 

 articulation, for the case of two- and three-sound syllables. 



We are now in a position to consider the figure which best represents 



