Phonetic distance measurement system and related methods

Abstract

Phonetic distances are empirically measured as a function of speech recognition engine recognition error rates. The error rates are determined by comparing a recognized speech file with a reference file. The phonetic distances can be normalized to earlier measurements. The phonetic distances/error rates can also be used to improve speech recognition engine grammar selection, as an aid in language training and evaluation, and in other applications.

What is claimed is: 
     
         1 . A method of generating a phonetic distance matrix comprising:
 determining a plurality of error occurrences by comparing a recognized speech file with a reference file;   determining a plurality of error rates corresponding to the plurality of error occurrences;   determining a plurality of phonetic distances as a function of the plurality of error rates; and   outputting a phonetic distance matrix based on the plurality of phonetic distances.   
     
     
         2 . The method of  claim 1 , wherein the plurality of error occurrences includes a plurality of substitution, insertion and deletion error occurrences and the plurality of error rates includes a corresponding plurality of substitution, insertion and deletion error rates. 
     
     
         3 . The method of  claim 1 , wherein determining the plurality of error rates includes dividing the plurality of error occurrences by a total number of phonetic element occurrences in the reference file. 
     
     
         4 . The method of  claim 1 , wherein determining the plurality of phonetic distances and outputting the phonetic distance matrix includes normalizing the phonetic distances to minimize a total separation between the phonetic distance matrix and an existing phonetic distance matrix. 
     
     
         5 . The method of  claim 4 , wherein normalizing the phonetic distances to minimize the total separation between the phonetic distance matrix and an existing phonetic distance matrix includes using a mapping function with three normalization coefficients. 
     
     
         6 . The method of  claim 5 , wherein the mapping function is:
 Phonetic Distance i,j =α 1 +(α 2 /(Error Rate i,j −α 3 ));   wherein i and j are indices of the phonetic elements, and α 1 , α 2  and α 3  are the three normalization coefficients.   
     
     
         7 . The method of  claim 6 , wherein the separation between the phonetic distance matrix and the existing phonetic distance matrix is defined as:
 L(α 1 , α 2 , α 3 )=Σ i,j (Existing Phonetic Distance i,j −Phonetic Distance i,j ) 2 .   
     
     
         8 . The method of  claim 1 , further comprising generating the recognized speech file by processing, with a speech recognition engine, an audio file of a speaker reading contents of the reference file. 
     
     
         9 . The method of  claim 8 , further comprising generating the audio file. 
     
     
         10 . The method of  claim 1 , wherein determining a plurality of error occurrences includes comparing a plurality of recognized speech and reference files. 
     
     
         11 . The method of  claim 10 , wherein the plurality of recognized speech files correspond to audio files of a plurality of different speakers. 
     
     
         12 . The method of  claim 10 , wherein the plurality of recognized speech files are generated by a plurality of different speech recognition engines. 
     
     
         13 . A phonetic distance measurement system comprising:
 a reference file;   a recognized speech file;   a comparison module configured to determine a plurality of error occurrences by comparing the recognized speech file and the reference file;   an error rate module configured to determine a plurality of error rates corresponding to the plurality of error occurrences; and   a measurement module configured to determine a plurality of phonetic distances as a function of the plurality of error rates.   
     
     
         14 . The system of  claim 13 , further comprising a dictionary, wherein the comparison module is further configured to access the dictionary to identify phonetic elements in the reference file and recognized speech file prior to determining the plurality of error occurrences. 
     
     
         15 . The system of  claim 13 , wherein the plurality of error occurrences the comparison module is configured to determine include substitution error occurrences, insertion error occurrences and deletion error occurrences. 
     
     
         16 . The system of  claim 15 , wherein the comparison module is further configured to identify the plurality of substitution error occurrences by corresponding phonetic element pairs and the insertion and deletion error occurrences by corresponding phonetic elements. 
     
     
         17 . The system of  claim 13 , wherein the measurement module is further configured to normalize the phonetic distances.