13. A speech recognition method comprising: receiving a succession of acoustic descriptions, each of which describes one of a succession of sounds from an utterance to be recognized; storing a plurality of acoustic models; storing in association which each such model a separate word score for each of a plurality of vocabulary words, which score indicates the probability that its associated word corresponds to the utterance to be recognized given that the score's associated acoustic model is found to match an acoustic description from that utterance; matching one of said acoustic models with each of said acoustic descriptions based on the relative closeness of said models with said descriptions; calculating a total word score for each of said vocabulary words by combining the word scores for that word associated with each of the acoustic models which matches one of said acoustic descriptions; and using the total word score produced for each vocabulary word to determine which of said vocabulary words most probably corresponds to the utterance to be recognized; in which: the word score for each vocabulary word stored in association with each acoustic model corresponds to a logarithm of the probability of that word corresponding to the utterance to be recognized given that its model is found to match an acoustic description from that utterance; and said calculating of a total word score for each vocabulary word includes adding the word scores associated with that word from each of the selected acoustic models.
13. A speech recognition method comprising: receiving a succession of acoustic descriptions, each of which describes one of a succession of sounds from an utterance to be recognized; storing a plurality of acoustic models; storing in association which each such model a separate word score for each of a plurality of vocabulary words, which score indicates the probability that its associated word corresponds to the utterance to be recognized given that the score's associated acoustic model is found to match an acoustic description from that utterance; matching one of said acoustic models with each of said acoustic descriptions based on the relative closeness of said models with said descriptions; calculating a total word score for each of said vocabulary words by combining the word scores for that word associated with each of the acoustic models which matches one of said acoustic descriptions; and using the total word score produced for each vocabulary word to determine which of said vocabulary words most probably corresponds to the utterance to be recognized; in which: the word score for each vocabulary word stored in association with each acoustic model corresponds to a logarithm of the probability of that word corresponding to the utterance to be recognized given that its model is found to match an acoustic description from that utterance; and said calculating of a total word score for each vocabulary word includes adding the word scores associated with that word from each of the selected acoustic models. 14. A speech recognition method as described in claim 13 in which: all of the separate word scores associated with each acoustic model are stored in an array; all of the total word scores for each vocabulary word are stored in a corresponding array; and said calculating of said total word scores includes adding the elements of the word score array associated with each acoustic model found to match an acoustic description from the utterance to be recognized with the corresponding element of the total word score array to derive an updated total word score array.