INTELLIGIBILITY AND CONFUSABILITY OF VOWELS AND DIPHTHONGS UNDER VARIOUS CONDITIONS OF QUIET AND NOISE

Sixteen English vowels and diphthongs were recorded by 4 male and 4 female speakers. For each vowel and diphthong, 120 responses were obtained from a panel of 6 phonetically trained listener at several levels of noise and quiet; each of 5 levels of noise were matched for listening difficulty with 5 levels of quiet. The levels of difficulty ranged from approximately 25 to 85% correct. The results on vowel-diphthong intelligibility support the conclusions that vowels and diphthongs (1) are significantly different in intelligibility, (2) have a fairly stable order of intelligibility, similar in noise and quiet and among the 8 speakers, though more stable among speakers of the same sex, (3) improve in intelligibility at different rates as listening conditions are improved, and (4) are more intelligible from male speakers. In regard to vowel and diphthong confusability, results support the conclusions that (1) a great many significant confusions exist among the vowels and diphthongs under fairly difficult listening conditions, (2 0 at least one significant confusion exists for each vowel and diphthong, (3) each vowel and diphthong is a significant confusion for at least one other vowel or diphthong, and (4) confusions bear a reciprocal relationship to one another.