14. The method of claim 1 , wherein said step (a) includes the steps of: (a-1) judging each frame as voiced or unvoiced; (a-2) judging, as a speech sub-block, every portion which includes a voiced portion of at least one frame and which is laid between unvoiced portions longer than a predetermined number of frames; and (a-3) judging, as a speech block, a series of at least one speech sub-block including a final sub-block, in which an average power of a voiced portion in said final sub-block is smaller than an average power of said final sub-block multiplied by a constant, wherein said step (c) includes a step of judging every speech sub-block as said portion of the input speech, judging a speech block including an emphasized speech sub-block as a portion of summarized speech, and outputting the portion of summarized speech.
14. The method of claim 1 , wherein said step (a) includes the steps of: (a-1) judging each frame as voiced or unvoiced; (a-2) judging, as a speech sub-block, every portion which includes a voiced portion of at least one frame and which is laid between unvoiced portions longer than a predetermined number of frames; and (a-3) judging, as a speech block, a series of at least one speech sub-block including a final sub-block, in which an average power of a voiced portion in said final sub-block is smaller than an average power of said final sub-block multiplied by a constant, wherein said step (c) includes a step of judging every speech sub-block as said portion of the input speech, judging a speech block including an emphasized speech sub-block as a portion of summarized speech, and outputting the portion of summarized speech. 17. The method of claim 14 , wherein said step (b) includes a step of calculating each normal-state likelihood for respective speech sub-blocks based on said normal-state appearance probabilities; and wherein said step (c) includes the steps of: (c-1) calculating a likelihood ratio of said emphasized-state likelihood to said normal-state likelihood for each said speech sub-block; (c-2) calculating a total duration by accumulating durations of each said speech block including a speech sub-block in a decreasing order of said likelihood ratio; and (c-3) deciding said speech blocks as portions to be summarized, at which a total duration of provisional portions is equal or approximate to a predetermined summarization time, or a summarization ratio is equal or approximate to a predetermined summarization ratio.