Analysis and optimization of speech intelligibility

We develop signal processing methods that ensure better speech intelligibility and less listening effort in a wide variety of applications. The technical transmission of speech is often compromised by superimposed reverberation and background noise, for example in the context of railway station announcements, mobile telephony or in-car infotainment systems. In media productions and broadcasting, deciding whether certain parts of speech are sufficiently intelligible for listeners is often a subjective matter. Fraunhofer IDMT’s software solutions analyse speech and sound according to objective measurement criteria and in real time – even in environments with variable acoustics.

Through our expertise in the field of signal processing and audio system technology, the quality of speech intelligibility can be measured and optimized. This allows media libraries, streaming services or providers of communication services to offer their customers added value, such as alternative soundtracks with better intelligibility or personalized solutions in end devices. Methods based on machine learning are used to identify audio signals containing speech, measure them in terms of their intelligibility and, if necessary, process them using our source separation algorithms. In this way, for example, dialogue in a media production can be accentuated even when background acoustics are complex and contain music or sound effects. In conference or telephone applications, speech signals can be automatically adjusted to ambient noise by means of adaptive signal processing. By taking into consideration recent findings from hearing research, with our solutions we can achieve an individually optimized sound experience for people with and without hearing impairments.

How to improve speech intelligibility

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What exactly do we mean when we talk about »better speech intelligibility«? Dr. Jan Rennies-Hochmuth explains how the analysis, evaluation and improvement of speech intelligibility works.

Telecommunication and consumer electronics


SI-Live – Real-time monitoring of speech intelligibility

Optimal speech transmission and smooth transitions between interlocutors in telephone calls and video conferences are important for high user acceptance.



Software solution for real-time optimization of speech intelligibility in noisy environments


The hearable for the smart industrial workplace

A small, in-ear hearable for better human-machine interaction – a big task for a little earbud.


If technical speech transmission is compromised by superimposed reverberation and background noise, we can improve the speech signal with the help of adaptive signal processing. Especially when it matters, for example in command centres, it is important that every word is heard and error rates kept low.


  • Command centres
  • Public address systems
  • Communication systems

Broadcasting and media production


Press Release / 23.5.2022

Seeing Speech

New algorithms from Fraunhofer IDMT form the basis for the »Dialogue Detection« in Steinberg Media Technologies’ latest version of its audio post-production software Nuendo. 


Presseinformation / 4.11.2021

Better understanding

Tonmeistertagung 2021: Fraunhofer IDMT presents solutions for analysing, evaluating and improving speech intelligibility.


Press Release / 10.12.2020

Red when mumbling!

Intelligibility Meter enables objective measurement and display of speech intelligibility in media productions


SITA – Better sound, less noise!

SITA addresses the main factors for poor speech intelligibility along the whole distribution chain and aims to eliminate existing barriers for the widest possible variety of target groups, applications and hearing scenarios with the help of innovative software technologies.

On-demand services

Speech signals can be improved not only during media production but afterwards too. In this way, users can adjust audio playback to their individual requirements, for example when streaming or in their media libraries.


  • Streaming
  • Media libraries

Oldenburg Branch for Hearing, Speech and Audio Technology HSA

Founded in 2008 as a project group, the Fraunhofer Institute for Digital Media Technology IDMT’s Branch for Hearing, Speech and Audio Technology HSA stands for market-oriented research and development with a focus on the following areas:

  • Speech and event recognition
  • Sound quality and speech intelligibility
  • Mobile neurotechnology and systems for networked healthcare

R&D-Services and Licencing

Please contact us in case you are interested in our expertise and services.