ARTICULATION TESTING METHODS 



837 



and for L — .80, m — 1.23. When observed values of /;/ become 

 consistently greater or less than this theoretical value, it must be 

 concluded that the assumptions underlying this statistical theory are 

 not valid. 



All of the above statistical relations are dependent upon the tacit 

 assumption that the chance of perceiving any sound correctly is 

 entirely independent of the other sounds present and also independent 

 of the number of other sounds present. It was shown in the previous 

 section that the articulation of the various sounds is, on the average, 

 independent of the other sounds in the syllables. On the other hand, 

 experiments have indicated that the articulation does depend upon 

 the number of sounds in the syllable. The sound articulation becomes 

 smaller when the number of sounds in the syllables increases beyond 

 three per syllable. 



The data from which this conclusion was drawn were taken from 

 three different experiments. In the first, three different transmission 

 systems were tested by using first the standard articulation lists and 

 then the vowel-consonant lists which are described in the last section. 

 When using the vowel list, the vowels only are considered and when 

 using the consonant list the consonants only are considered. These 

 lists together, then may be considered as composed of syllables having 

 only one sound. The syllable and sound articulations are the same 

 when using such lists. The comparison of the results obtained with 

 the two types of lists is shown in Table X. It will be seen that there 



TABLE X 

 Articulation for One- and Three-Sound Syllables 



is only a slight tendency for the sound articulation to be lower for 

 the three-sound syllable when compared with the one-sound syllable. 

 The differences are within the observational error in testing. 



In the second experiment a new list was constructed using the 



syllable forms con-vow and vow-con. The auxiliary circuit of the 



master reference system was tested with this list and also with the 



standard articulation list. The results are shown in Table XI. The 



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