What Is Accuracy Of TTS? How To Measure The Accuracy Of Tts?

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What is the accuracy of TTS? What can affect the accuracy of TTS? They are FAQs for those interested in TTS tools. Click on this post for a detailed answer!

Text to Speech,

Text-to-speech (TTS) tools have made notable advances in recent years. So it enables the conversion of written text into synthetic speech.

But what is the accuracy of TTS? Assessing its accuracy is vital to ensure that the audio output effectively represents the intended content.

So what factors affect the accuracy of TTS? And how to measure it? Let’s find out the answer with us!

How Text-To-Speech Works?

Text to Speech,

How TTS Works?

Simply put, TTS tools convert written text into speech.

First, the text is analyzed and broken down into linguistic parts. They include sentences, words, and phonemes. These parts are then assigned various audio parameters, such as pitch and duration.

Next, these parameters can generate a waveform representing the output voice. This waveform is then passed through a digital signal processing (DSP) tool to enhance the quality and make the sound more natural.

Finally, the enhanced waveform is played through speakers or headphones, allowing you to hear the converted text as speech.

What Is Accuracy Of TTS?

What Is Accuracy Of TTS?

TTS’s accuracy refers to how well the output voice matches the intended meaning and pronunciation of the input text.

A more accurate TTS tool will produce speech that sounds natural, speaks words correctly, and conveys the intended tone of the text.

Yet, the accuracy will not be the same in all cases and all tools but depends on the following factors:

Quality Of The Input Text

The quality of the input text, including grammar, spelling, and punctuation, can notably affect the accuracy of a TTS tool.

The TTS tool relies on language rules and models to convert written text into speech. Thus, if the input text has grammatical errors, such as incorrect sentence structure or word usage, the TTS tool may be challenging in producing coherent speech.

On the other hand, the well-punctuated text will facilitate the TTS process. Hence, the tool can interpret the desired meaning more accurately.

The Complexity Of The Language

If the text has a complex structure or uses difficult words, the TTS tool may have difficulty speaking them correctly. Similarly, if the text includes technical terms or jargon, the TTS tool may not know how to read them.

In general, simple words and sentences are easy for TTS tools to process and produce more accurate and natural voices.

TTS Technology

TTS accuracy depends on various technology-related things. One important thing is the quality of the language and database models used by the TTS tool.

These models have rules that help the system understand and speak words correctly. Thus, the output speech will be more accurate if it has good models.

Besides, advanced neural network models, such as deep learning, help TTS tools be better. These models can understand complex patterns in speech and make output speech sound more natural.

Types Of TTS Tools

Text to Speech,

Types Of TTS Tools

The following five TTS tool types are available:

  • Built-in TTS: Many devices (smartphones, computers, tablets, and Chrome) have built-in TTS features. Hence, it allows you to have text read aloud without needing other apps or tools.
  • Web-based tools: Some websites offer on-site TTS tools, helping you read web pages aloud.
  • TTS app: You can download the TTS app on tablets and smartphones. These apps often have extra features like text markup and optical character recognition (OCR).
  • Chrome engine: Chrome provides TTS tools like Read&Write and Snap&Read. You can use them on your Chromebook or any computer with the Chrome browser.
  • Specialized TTS software for computers: It provides TTS functions in other reading and writing tools.

How To Measure The Accuracy Of TTS?

Text to Speech,

How To Measure The Accuracy Of TTS?

To measure the accuracy of the TTS feature, you can self-assess the following:

  • Listen to the output and evaluate how well you understand it, how natural it is, and how accurate it is.
  • Compare different tools or versions of TTS and choose the one you think is better and more accurate.

On the other hand, the accuracy of a TTS tool is also measured by the Word Error Rate (WER). WER represents the percentage of errors for every 100 words in the copied text.

Lower WER indicates higher accuracy. For example, the copied text is 98% accurate with a 2% error rate.

Human measures provide valuable insights into the naturalness and intelligibility of output voices. Meanwhile, the WER method provides quantitative assessments of accuracy aspects.

Yet, we recommend measuring the accuracy of TTS according to your judgment and judgment rather than using specific numbers or formulas.

Limitations Of TTS

Text to Speech,

Limitations Of TTS

Although TTS tools have improved in producing more natural voices, some areas can be lacking. So what are they? Read on to learn more!


Naturalness includes factors such as:

  • Intonation
  • Rhythm
  • Stress
  • Expression of emotions in human speech

Despite efforts to mimic these elements, TTS tools may have difficulty reproducing the full range of natural variations and nuances in human speech.

Hence, the output of the TTS tool sounds mechanical or lacks the subtle signals that contribute to natural and expressive communication.

Thus, further progress is needed to bridge the gap between TTS and human-like naturalness.


As mentioned, although TTS tools have made notable progress in correctly speaking common words, they may still face challenges with some specialized words, names, or terms.

Unusual words, dialects, or context-dependent pronunciations can make TTS systems difficult. This issue arises from reliance on pre-existing dictionaries or pronunciation rules that may not cover all language variations.

Hence, TTS tools may mispronounce words, leading to inaccuracies in the output.

Context Understanding

TTS systems cannot often fully capture the meaning behind the text. In particular, homonyms, ambiguous phrases, and puns can confuse TTS systems, resulting in inaccurate or unnatural speech output.

Besides, TTS may have difficulty properly emphasizing certain words or phrases based on the intended context.


What is the accuracy of TTS? It refers to how similar the output voice is to the original text, including pronunciation, naturalness, and overall quality.

However, many factors can affect the accuracy of the TTS system, such as the quality of the input text, the complexity of the language, and the TTS tool itself.

Yet, continuous advances in TTS technology and language resources will improve the accuracy of TTS tools.

Thank you for reading!

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