How to measure the quality of a transcription for qualitative analysis

Transcrição 2024-06-30


The quality of a transcription is essential to ensure that the information is correctly understood. One of the most commonly used metrics to evaluate this quality is the Word Error Rate (WER). This article explores the importance of transcription quality, what WER is, evaluation metrics, factors affecting quality, how to improve transcription, a comparison of different tools, and the importance of human review.

Main Conclusions

  • The quality of the audio and the spoken language are crucial for transcription accuracy.

  • The Word Error Rate (WER) is a fundamental metric for evaluating the quality of transcriptions.

  • There are three main types of errors in transcriptions: substitutions, insertions, and deletions.

  • Advanced techniques and continuous training can significantly reduce transcription errors.

  • Human review is indispensable for correcting errors and improving transcription accuracy.


Importance of Transcription Quality

Impact on Understanding

Transcription quality is crucial to ensure that the spoken content is correctly understood. Errors in transcription can lead to significant misunderstandings, especially in critical contexts such as business meetings or medical consultations.

Practical Applications

Accurate transcriptions are essential in various areas, such as:

  • Education: Facilitates access to the content of classes and lectures.

  • Legal: Ensures the accuracy of testimonies and hearings.

  • Media: Improves the accessibility of videos and podcasts.

Common Challenges

Achieving high-quality transcriptions faces several challenges, including:

  • Background noise in the audio.

  • Variations in accent and pronunciation.

  • Use of jargon and specific terminologies.

Transcription quality should not be neglected, as it directly impacts the effectiveness of communication and the accessibility of information.


What is Word Error Rate (WER)

Definition and Formula

The Word Error Rate (WER) is a standard metric used to evaluate the accuracy of automatic transcriptions. It measures the proportion of incorrectly transcribed words in relation to the total words in the original transcription. The formula for calculating WER is:


  • I: Insertions

  • D: Deletions

  • S: Substitutions

  • N: Total number of words in the original transcription

Types of Errors Considered

The errors considered in calculating WER are classified into three main categories:

  1. Insertions (I): Words added that are not present in the original audio.

  2. Deletions (D): Words omitted that are present in the original audio.

  3. Substitutions (S): Incorrectly transcribed words.

Practical Examples

For illustration, consider the original transcription: "The cat is on the roof." If the automatic transcription is "The cat on the roof," we have:

  • Deletion: 1 (the word "is" was omitted)

  • Insertion: 0

  • Substitution: 0

In this case, the WER would be:

Understanding WER is essential for improving the quality of automatic transcriptions and ensuring effective communication.


Transcription Evaluation Metrics


Accuracy measures the proportion of correctly transcribed words in relation to the total words in the transcription. It is a crucial metric for evaluating the quality of a transcription. The higher the accuracy, the better the transcription reflects the original audio.


Recall, or revocation, evaluates the transcription system's ability to capture all the words from the original audio. High recall indicates that few words were omitted in the transcription.

F1 Score

The F1 score is the harmonic mean between accuracy and recall, offering a balanced view of the transcription system's performance. It is especially useful when it is necessary to consider both accuracy and recall equally.

The combination of these metrics provides a comprehensive evaluation of transcription quality, allowing for the identification of areas for improvement and comparison of different transcription systems.


Factors Affecting Transcription Quality

Audio Quality

Audio quality is one of the main factors influencing transcription accuracy. Audios with background noise, distortions, or low clarity can result in inaccurate transcriptions. It is essential to use high-quality recording equipment and quiet environments to capture the audio.

Spoken Language

The spoken language also plays a crucial role in transcription quality. Some languages have more available resources and trained models, which can improve accuracy. Additionally, regional accents and dialects can introduce variations that make automatic transcription difficult.

Context and Vocabulary

The context and vocabulary used in the audio are equally important. Technical terms, jargon specific to an area, and proper names can be challenging for transcription models. Providing a clear context and, if possible, a personalized vocabulary can help improve transcription accuracy.

Transcription quality is directly proportional to audio clarity, familiarity with the language, and the context provided. Improving these aspects can result in more accurate and reliable transcriptions.


How to Improve Transcription Quality

To reduce errors in transcriptions, it is essential to adopt some best practices. Adjusting the audio quality is one of the first steps, ensuring that the sound is clear and free of background noise. Additionally, using personalized vocabularies can help improve accuracy, especially in areas with specific terminologies.

The use of advanced transcription models, such as those based on deep neural networks, can significantly increase transcription quality. These models are trained with large volumes of data and can better handle variations in speech and accents.

Continuous improvement of transcription models is fundamental. This can be done through continuous training with new data, adjusting the models to better meet the specific needs of each application. Regular model updates ensure that they remain effective and accurate.

Transcription quality is a crucial factor for various applications, from video subtitling to call analysis in call centers. Improving this quality can bring significant benefits in terms of understanding and efficiency.


Comparison of Different Transcription Tools

There are several transcription tools available in the market, each with its own features and functionalities. Some of the most popular include:

  • Amazon Transcribe: Known for its ability to generate multiple versions of a transcription and assign confidence scores to each one.

  • Google Cloud Speech-to-Text: Offers support for multiple languages and is widely used for its accuracy and integration with other Google services.

  • IBM Watson Speech to Text: Stands out for its customization capability and support for different industry sectors.

  • Microsoft Azure Speech to Text: Integrated with the Azure ecosystem, known for its scalability and security.

  • Meetpulp: Our high-reliability solution for qualitative analysis that not only allows high-reliability transcription but also lets you do much more with your transcriptions.

Below is a comparative table of the main advantages and disadvantages of each tool:




Amazon Transcribe

High accuracy, multiple versions of transcription

High cost

Google Cloud Speech-to-Text

Support for multiple languages, integration with Google services

Can be complex to configure

IBM Watson Speech to Text

High customization, support for different sectors

Interface can be less intuitive

Microsoft Azure Speech to Text

Scalability, security, integration with Azure

Requires prior knowledge of the Azure ecosystem


Transcription accuracy, integrated tools for qualitative analysis

More recent tool, may have some bugs


Case studies show that the choice of transcription tool can significantly impact the efficiency and accuracy of transcriptions. For example, a media company that uses Google Cloud Speech-to-Text managed to reduce transcription time by 30%, while a call center that adopted Amazon Transcribe improved the sentiment analysis of their calls by 25%.

The choice of transcription tool should consider not only the cost but also the accuracy, ease of integration, and specific needs of the sector.



Introduction to Meetpulp

Meetpulp is the latest qualitative analysis tool, which allows not only transcribing interviews and other audios but also obtaining summaries, sentiment analyses, finding codes in interviews, and tagging excerpts with these codes.

But how good is Meetpulp’s transcription?
The quality of transcription will always depend on the language and audio quality, making it difficult to determine a system's capability.

To test Meetpulp’s transcription quality, several audiobooks and their respective texts were used to transcribe and have a point of comparison. The results after several books and stories in Portuguese showed an average WER of 4.85%, that is, a 95.15% accuracy. However, this does not tell the whole story.

By analyzing the errors, it was also possible to see that most of the errors fell into one of the following categories:

  • Numbers - one of the texts writing out the numbers while the other wrote them together

  • Separations - some words appeared without the space separating them

  • Spelling - some errors due to different ways of spelling a word in Brazilian Portuguese and European Portuguese

For the context of qualitative analysis, although accurate transcription is always essential, these issues should not significantly affect the results, meaning the identified errors can be disregarded in this situation.

You can start transcribing, summarizing, and finding codes in your interviews today with Meetpulp by visiting


Importance of Human Review in Transcription

Error Correction

Human review is essential for correcting errors that go unnoticed by automatic systems. Even with technological advances, human intervention ensures superior accuracy.

Enhancement of Accuracy

Human reviewers can identify nuances and contexts that machines still cannot capture. This results in a transcription more faithful to the original content.

Specific Cases

There are situations where automatic transcription fails, such as in audios with noise or technical vocabulary. In these cases, human review is indispensable to ensure transcription quality.

The combination of technology and human review is the key to achieving high-quality transcriptions.



The quality of a transcription is fundamental for various applications, from virtual assistants to voice recognition systems in industrial environments. The Word Error Rate (WER) metric stands out as an essential tool for evaluating this quality, providing a clear view of transcription accuracy. Understanding the types of errors—substitutions, insertions, and deletions—and how they impact WER is crucial for continuously improving transcription systems. While WER provides a valuable quantitative measure, it is also important to consider other factors, such as audio quality and speech context, for a more holistic evaluation. Ultimately, the pursuit of a perfect transcription is a continuous process of refinement and adaptation to the specific needs of each application.


Frequently Asked Questions

What is Word Error Rate (WER)?

Word Error Rate (WER) is a metric used to evaluate the accuracy of an audio transcription. It calculates the error rate by comparing the generated transcription with the original text.

What types of errors are considered in WER?

The types of errors considered in WER are substitutions (one word is replaced by another), insertions (extra words are added), and deletions (words are omitted).

How is WER calculated?

WER is calculated by the formula: 

 where I is the number of insertions, D is the number of deletions, S is the number of substitutions, and N is the total number of words in the original text.

Why is audio quality important for transcription?

Audio quality is crucial because background noise, low recording quality, and other factors can increase the error rate in transcription.

What are the transcription evaluation metrics besides WER?

Besides WER, other common metrics are accuracy, recall, and F1 score, which help evaluate different aspects of transcription quality.

How can I improve the quality of my transcriptions?

To improve transcription quality, you can use error reduction techniques, adopt advanced speech recognition models, and continuously train the models. Optionally, you can use tools that allow better results, such as Meetpulp.