Understanding Speech-to-Text Accuracy

When we talk about transcription accuracy, the numbers can be deceiving. Let's demystify what accuracy metrics really tell us.

Word Error Rate (WER): The Industry Standard

The most common metric for measuring transcription accuracy is Word Error Rate. It calculates the percentage of words that were incorrectly transcribed, including:

• Substitutions: Words replaced with different words
• Insertions: Extra words added that weren't spoken
• Deletions: Words that were spoken but not transcribed

A 5% WER means that, on average, 5 out of every 100 words contain some error. For a 1,000-word transcript, that's about 50 potential corrections needed.

Factors That Affect Accuracy

Not all audio is created equal. Several factors can significantly impact how well any transcription system performs:

Audio Quality

Clean, studio-quality audio can achieve WERs below 3%. Phone recordings or noisy environments might see WERs of 10-15% or higher.

Speaker Characteristics

Accents, speaking pace, and clarity all play a role. Heavy accents or very fast speech can increase error rates.

Domain-Specific Vocabulary

Technical jargon, proper nouns, and industry-specific terms are often challenging. Custom vocabulary training can help.

Beyond Raw Accuracy

A 95% accurate transcript isn't automatically usable. The nature of errors matters too:

• Errors in names or key terms are more impactful than minor words
• Context-breaking errors require more effort to fix
• Consistent errors can be batch-corrected; random errors cannot

At DeepScribe, we focus not just on headline accuracy numbers, but on producing transcripts that minimize editing time and maximize readability.