Speech Intelligibility

Speech intelligibility

Speech intelligibility refers to the 'understandability' of speech, and the ability to use speech to communicate effectively in everyday situations. It can be affected by many factors, including pronunciation accuracy, audibility and speaking rate.

The Speech Intelligibility Scorer uses speech recognition and text to speech technology to:

Provide a measure of speech intelligibility.
Provide a measure of audibility.
Provide a measure of speaking rate.
Provide example pronunciations of any letter, word, number or sentence.
Highlight unintelligible and problematic words.
Speech Intelligibility Scorer

How the Speech Intelligibility Scorer works

To score your speech intelligibility, simply enter any text and read it out loud. As you speak, the recognised words are scored from 0 to 100 and highlighted in green. Any unrecognised words are highlighted in red. Once all of the words have been highlighted, the following results are displayed:

Speech intelligibility score

Speech intelligibility is a measure of how easily speech can be understood and is expressed as a percentage. The speech intelligibility scores are categorised as:

Intelligibility description Intelligibility score
Unintelligible 0%
Poor 10% - 30%
Fair 30% - 50%
Good 50% - 75%
Excellent 75% - 100%


In order to understand speech it must be audible. Audibility depends on the loudness of speech and is measured in decibels (dB). The human hearing range goes from 0 dB to 120-140 dB:

Condition Audibility (dB)
Hearing threshold 0 dB
Whisper 30 dB
Normal conversation 60 dB
Shout 90 dB
Pain threshold 120 -140 dB

Speech rate

Speech rate is the term given to the speed at which we speak and is expressed as the number of words spoken per minute (WPM). Depending on the type of speech, the rate may vary from 100 WPM to over 400 WPM:

Type of speech Speech rate (WPM)
Slow speech 100 - 110 WPM
Conversational speech 120 - 200 WPM
Audiobooks and podcasts 150 - 160 WPM
Auctioneers and commentators 250 - 400 WPM

Supported languages

The Speech Intelligibility Scorer uses the computer's default speech recognition engine. There are several speech engines available for Windows:

  • US English
  • UK English
  • French
  • Spanish
  • German
  • Japanese
  • Traditional Chinese
  • Simplified Chinese

If your preferred language is not installed, you can obtain additional languages by installing the appropriate Windows language pack.

Who should use the Speech Intelligibility Scorer?

The Speech Intelligibility Scorer is an invaluable tool for anyone interested in the production of speech. It can be used by speech and language therapists or by their patients wishing to practice between sessions. It can also be used as an aid to learning a foreign language.

System requirements

Operating Systems Windows 10, 8, 7 and Vista
CPU Minimum 1 GHz Intel® Pentium® or equivalent
Memory Minimum 1 GB of RAM
Storage 100 MB of free hard disk space
Microphone A USB headset microphone is recommended

Download free trial

The Speech Intelligibility Scorer is now only available as part of the icSpeech Standard and Professional integrated applications.

To download a free trial of icSpeech Standard Edition, simply click on the download button and follow the installation instructions.

For best results, we recommend using a USB headset microphone. See our range of recommended microphones.

icSpeech Standard Edition
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"This software is like having a very patient, native English speaker listen to you talk and tell you how well they understood you. With only a few hours of use, your self-confidence with spoken English will be greatly increased, continued use will lead to amazing results."

Antony Alexander
Thanh Tuu Tri English Center


"We compared the ratings from a newly developed piece of software, the Speech Intelligibility Scorer, against intelligibility ratings from naïve human listeners. We used audio files recorded from adults with a range of speech and voice impairments. Results showed a positive correlation between scores from the software and those from human listeners.

Therefore, ratings provided by the Speech Intelligibility scorer are related to how intelligible individuals are in real life. This supports the use of the scorer as a tool to effectively measure intelligibility."

Department of Clinical Language Sciences, University of Reading, Reading, UK.


"I have purchased the 'Pronunciation Coach' and 'Speech Intelligibility' on 9th Feb 2015. These products are brilliant. They replace speech therapists and I can work on my own time. The pressure of pronouncing the words correctly is immensely reduced as I can use these tools to assist me. I feel more hopeful and confident. I am still practising to differentiate between 'Louise' & 'Lewis'.

Thank you."

Rethinakumari Katamuthu,