複数個帯域濾波器による明瞭度試験結果について (<音声特集号>)

抄録

Speech sound articulations, each vowel articulation and confusions between consonants obtained by the articulation tests on speech transmission systems utilizing two or three bandpass filters which have passbands corresponding approximately to the bands of formants in Japanese vowels are discussed here. (1) Sound Articulation : Maximum sound articulations of the systems were calculated by the method of calculation using frequency importance function of articulation, and the results were compared with the measured values. In a system possessing an isolated passing band in high frequency region as the system corresponding to vowel /i/, a significant disagreement is observed. This disagreement seems to indicate that the contribution of the frequence band in question to the articulation is greater when it is in co-existence with the intermediate frequency band than while it is isolated. (2) Vowel Articulation : For a transmission system possessing passbands corresponding to the formants of a vowel, the articulation of the vowel obtained does not show much improvement over the articulation of other vowels after passing the same system. For systems corresponding to vowels other than /i/, the articulations of all the vowels obtained after passing each one of the systems are all above 0. 8, whereas the values obtained for the system corresponding to /i/ are all much lower than these values. This seems to indicate that discrimination between all vowels does not depend upon the recognition of the position of formants but on the detection of the difference in frequency spectrum with in a limited frequency band. (3) Confusion between Consonants When the consonants are grouped as (1)k, p, t, s, h, etc. , (2)g, b, d, r, z, etc. , and (3)m, n, w, y, etc. , the confusion between the consonants of the same group is great, whereas the confusion between the consonants belonging th different groups is rare. This seems to indicate that the consonants belonging to each of the groups possess some characteristic property to that group which is not lost by limitation of passing band.