To automatically detect and automatically correct in a reproduced speech, defective portions related to plosives such as existence or absence of plosive portions, phoneme lengths of aspirated portions that continue after the plosive portions or defective portions related to amplitude variations of fricatives. Speech wherein consonants and unvoiced vowels are unclear and discordant is input into a speech enhancement apparatus according to the present invention. In the speech enhancement apparatus, the speech is split into phonemes and each phoneme is classified into any one of an unvoiced plosive, a voiced plosive, an unvoiced fricative, a voiced fricative, an affricate, and an unvoiced vowel. Each phoneme is corrected according to a determination of necessity of correction of each phoneme to obtain an output of the speech wherein the consonants and the unvoiced vowels are clear and not discordant.
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