ARTICULATION TESTING METHODS 835 



in speech. The analysis was not extensive enough to draw conclusions 

 as to the effects of particular sound combinations upon the articulation 

 of individual speech sounds. 



Approximately 40 per cent of the syllables that occur in English 

 are of the con-vow-con type. About 34 per cent are of the con-vow, 

 and vow-con type. The syllables, including the compounds, such as, 

 con-con-vow, vow-con-con, con-vow-con-con, and cbn-con-vow-con, 

 make up about 16 per cent of the syllables of English. Since, as 

 pointed out above, the interpretation of the consonant compounds 

 depends primarily upon only one of the consonants, the latter syllables 

 may be grouped in the two former classes, which then constitute some 

 90 per cent of English. Of the remaining syllables, 7 per cent consist 

 of a single vowel, so that the more complex syllable forms constitute 

 only 3 per cent of English.^ Since 97 per cent of the syllables of 

 English are included in the one, two and three letter forms, there is 

 little reason to include the more complex syllable forms in order to 

 represent speech, when as has been previously stated, they are unde- 

 sirable from a testing standpoint. As will be shown in a later para- 

 graph, one, two and three-letter syllables all yield equal values of 

 articulation for the various speech sounds. Since the three-letter 

 syllables require a smaller testing time for a given number of called 

 sounds, the other syllable forms were excluded from the testing lists. 



Having shown that the standard technique gives, for the various 

 sounds, data that are representative of speech, the question now arises 

 as to the best figure that may be computed from the data obtained 

 with this technique, in order to best represent the speech transmission 

 ability of the system under test. Before discussing this, it is necessary 

 to consider some probability relations existing between the quantities 

 entering into the calculation of such a figure. 



Statistical Relations 

 The syllable articulation S when expressed as the ratio of the 

 number of successes (correct interpretations of the syllables) to the 

 number of trials (syllables called) is the chance of perceiving a syllable 

 correctly. Also, if a similar ratio is used for the sound articulation 

 L, the vowel articulation V, and the consonant articulation C, then 

 these letters represent the probability of perceiving correctly a funda- 

 mental sound, a vowel sound or a consonent sound, respectively. 

 If a syllable contains only one fundamental sound, then it is obvious 



that 



S= L. (3) 



8 These data were obtained from Godfrey Dewey's book "Relative Frequency 

 of English Speech Sounds," Harvard University Press, 1923. 



