1. A speech recognition system, comprising: a distance calculation unit which generates a distance value between speech features, inputted sequentially, and each acoustic model; an acoustic lookahead unit which generates an acoustic lookahead value by using the distance value previously generated by the distance calculation unit, in parallel with generation of the distance value by the distance calculation unit; a word string matching unit which performs word matching by using the distance value previously generated by the distance calculation unit and the acoustic lookahead value previously generated by the acoustic lookahead unit to thereby generate a recognition result, in parallel with generation of the distance value by the distance calculation unit and generation of the acoustic lookahead value by the acoustic lookahead unit.
1. A speech recognition system, comprising: a distance calculation unit which generates a distance value between speech features, inputted sequentially, and each acoustic model; an acoustic lookahead unit which generates an acoustic lookahead value by using the distance value previously generated by the distance calculation unit, in parallel with generation of the distance value by the distance calculation unit; a word string matching unit which performs word matching by using the distance value previously generated by the distance calculation unit and the acoustic lookahead value previously generated by the acoustic lookahead unit to thereby generate a recognition result, in parallel with generation of the distance value by the distance calculation unit and generation of the acoustic lookahead value by the acoustic lookahead unit. 2. The speech recognition system, according to claim 1 , further comprising: distance value buffers which store distance values generated by the distance calculation unit; and acoustic lookahead value buffers which store acoustic lookahead values generated by the acoustic lookahead unit, wherein in each of the distance value buffers, operations of writing the distance value from the distance calculation unit, reading out the distance value to the acoustic lookahead unit, and reading out the distance value to the word string matching unit are performed, in each of the acoustic lookahead value buffers, operations of writing the acoustic lookahead value from the acoustic lookahead unit and reading out the acoustic lookahead value to the word string matching unit are performed, wherein, at any point in time, the distance value buffer in which the distance value from the distance calculation unit is written, the distance value buffer from which the distance value to the acoustic lookahead unit is read out, and the distance value buffer from which the distance value to the word string matching unit are read out, are different from one another, and the acoustic lookahead value buffer in which the acoustic lookahead value from the acoustic lookahead unit is written and the acoustic lookahead value buffer from which the acoustic lookahead value to the word string matching unit is read out are different from each other.