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Word error rate

As explained in Natural Language Processing in Action, Second Edition

Word error rate is the proportion of word-level transcription errors relative to the reference transcription.

Word error rate (WER) measures the proportion of words that an automatic speech-to-text system transcribes incorrectly against a reference transcription. It turns transcription quality into a comparable metric for choosing an STT system. section 12.7.4

Comparing speech-to-text systems

A benchmark comparison reports mean WERs of 60% for Kaldi, 31% for wav2vec 2.0, and 12% for Whisper across AI, phone, meeting, video, and finance datasets. The domain-specific scores show why a single average may not represent every deployment. section 12.7.4

Listing 12.3 TTS word error rate
|             | AI   | Phone   | Meeting   | Video   | Finance   | Mean   |
|:------------|:-----|:--------|:----------|:--------|:----------|:-------|
| Kaldi       | 66%  | 78%     | 54%       | 69%     | 35%       | 60%    |
| wav2vec 2.0 | 33%  | 41%     | 39%       | 26%     | 17%       | 31%    |
| Whisper     | 6%   | 20%     | 19%       | 9%      | 5%        | 12%    |

Inspect the benchmark table to compare WER across models and speech domains. section 12.7.4

How Natural Language Processing in Action, Second Edition covers it

How deep it goes
Defines word-level transcription comparison and reports benchmark results, but does not detail the calculation procedure.
Examples
Uses AI, phone, meeting, video, and finance benchmark datasets to compare Kaldi, wav2vec 2.0, and Whisper.
What it assumes
Assumes familiarity with speech transcription and introduces quantitative comparison through benchmark datasets.
What you can do after
Evaluate STT systems using benchmark WERs and compare their performance across deployment-relevant speech domains.
How it connects
Connects speech-to-text, benchmark datasets, voice assistants, and models including Kaldi, wav2vec 2.0, and Whisper.

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