Method for online adaptation of pronunciation dictionaries

A method for recognizing speech is suggested wherein a lexicon (SL, CL) or a pronuniciation dictionary used for the recognition process is modified during the process of recognition starting with a starting lexicon (SL) and including after given numbers of steps of recognition ( 12 ) recognition related information (RRI) with respect to at least one recognition result ( 13 ) already obtained and wherein the process of recognition is then continued based on a modified lexicon (ML) as said current lexicon (CL).

FIG. 1 illustrates by means of a schematic block diagram the processing of an embodiment of the inventive method for recognizing speech 10 . In step 11 of the method 10 shown in FIG. 1 an incoming speech flow is received—for example continuously spoken speech—as a sequence of speech phrases . . . , Spj, . . . and pre-processed, in the sense of the filtering and/or digitizing process so as to obtain a corresponding sequence of representing signals . . . , RSj, . . . each of which being a combination of possible word or subword candidates . . . , W jk , . . . In the next step 12 the received speech is at least in part recognized using a current lexicon CL or dictionary being provided by step 17 which may be for the first recognition step for the current speaker the starting lexicon SL as provided from step 17 a and containing recognition enabling information REI. Additionally the recognition step 12 may also be based on language models LM as well as on hidden Markow models HMM which are supported by processing steps 18 and 19 . Then the result of the recognition process is provided in step 13 . The incoming speech flow as provided by step 11 and/or the recognition result for the speech flow as provided by step 13 are supplied to step 14 of determining recognition related information RRI, and in particular of determining the pronunciation variants used. In the next step 15 it is checked whether these pronunciation variants and the distinct recognition related information has been already included into the current lexicon CL. The missing information is then included and/or generalized throughout the whole lexicon to yield a modified lexicon ML on the basis of the current lexicon CL. In step 16 the modified lexicon ML is restored as the current lexicon CL for the next recognition step 12 . In contrast to the present invention in a recognition method 20 of the prior art there is no closed loop of processing the incoming speech as well as the recognition related data. The dictionary CL provided to the recognition process 22 in step 27 is a closed entity which is generated off-line in particular in advance of the whole recognition process 20 . The dictionary CL provided by step 27 is kept fixed during the performance of the recognition 22 . In step 21 the incoming speech is provided in a pre-processed form to the recognition step 22 . The recognition result is provided with the step 23 of FIG. 2 , but not further evaluated with respect to the dictionary or lexicon CL. Again hidden Markow models HMM and other language models LM are used and evaluated in the recognition step 22 and are provided by steps 28 and 29 respectively. In the off-line generation 27 of the dictionary CL based on the vocabulary provided in step 30 the pronounciation variants are generated in step 31 and supplied to the dictionary CL which then influences the recognition step 22 as described above.