2. The apparatus according to claim 1, wherein said third processing means comprises: first matching means, connected to said second processing means and said first memory means, for determining that the monosyllabic acoustic parameter component of the input speech, having a vowel characteristic phoneme maximally resembling one reference vowel pattern among the reference vowel patterns stored in said first memory means, belongs to a selected first category among the first categories which includes the one reference vowel pattern and for generating category data representing the selected first category.
2. The apparatus according to claim 1, wherein said third processing means comprises: first matching means, connected to said second processing means and said first memory means, for determining that the monosyllabic acoustic parameter component of the input speech, having a vowel characteristic phoneme maximally resembling one reference vowel pattern among the reference vowel patterns stored in said first memory means, belongs to a selected first category among the first categories which includes the one reference vowel pattern and for generating category data representing the selected first category. 4. The apparatus according to claim 2, wherein when a monosyllable of the input speech has the vowel characteristic of one of the contracted sound and the syllabic nasal sound, that is, excluding the basic vowels, said first matching means determines the selected first category among specific first categories which directly correspond to the contracted sound and the syllabic nasal sound and which are included in the first categories stored in said first memory means.