Word error rate Totally Explained

Everything about Word Error Rate totally explained

Word error rate (WER) is a common metric of the performance of a speech recognition system. The general difficulty of measuring performance lies in the fact that the recognized word sequence can have a different length from the reference word sequence (supposedly the correct one). The WER is derived from the Levenshtein distance, working at the word level instead of the phoneme level.
This problem is solved by first aligning the recognized word sequence with the reference (spoken) word sequence using dynamic string alignment.
Word error rate can then be computed as:
ť

WER = frac

There is some debate, however, as to whether Hunt’s formula may properly be used to assess the performance of a single system, as it was developed as a means of comparing more fairly competing candidate systems. A further complication is added by whether a given syntax allows for error correction and, if it does, how easy that process is for the user. There is thus some merit to the argument that performance metrics should be developed to suit the particular system being measured.
   Whichever metric is used, however, one major theoretical problem in assessing the performance of a system, is deciding whether a word has been “mis-pronounced” for example does the fault lie with the user or with the recogniser. This may be particularly relevant in a system which is designed to cope with non-native speakers of a given language or with strong regional accents.
   The pace at which words should be spoken during the measurement process is also a source of variability between subjects, as is the need for subjects to rest or take a breath. All such factors may need to be controlled in some way.
   It is generally agreed that performance accuracy at a rate below 95% isn't acceptable, but this again may be syntax and/or domain specific, for example whether there's time pressure on users to complete the task, whether there are alternative methods of completion, and so on.
   The term "Single Word Error Rate" is sometimes used to refer to the percentage of incorrect recognitions for each different word in the system vocabulary.

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