System with speaking-rate-adaptive transition values for determining words from a speech signal

A system for determining words of a predetermined vocabulary from a speech signal, comprising

• first means for picking up the speech signal and for supplying a sequence of digital test signals,
• second means for storing sequences of reference signals which correspond to the words of the vocabulary,
• third means which are coupled to the first and the second means in order to compare the test signals with first reference signals so as to form a score for each first reference signal which is dependent on the difference between the test signal and the first reference signal, the first reference signal being identical to or a neighbour, in a predetermined manner, of a second reference signal within the relevant sequence with which a comparison has been successfully performed for the preceding test signal, the third means being arranged to increment, in dependence on the distance from said second reference signal, the score by a transition value which is dependent on the probability of transition,
• fourth means for summing the incremented scores for each sequence of reference signals compared with successive test signals, and for determining an optimum sequence having the smallest sum of the incremented scores and for outputting the word or the words associated with said optimum sequence,
• characterized in that there are provided fifth means for changing the transition values into new transition values for subsequent comparisons, in dependence on the deviation between the length of the speech signal wherefrom the test signals compared with the optimum sequence of reference signals are derived and the length of the optimum sequence of reference signals.