Tobias Hübschen


M. Sc. Tobias Hübschen

Room D-016
Kaiserstraße 2, 24143 Kiel, Germany
Phone: +49 431 880-6129
Telefax: +49 431 880-6128
E-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.

Research: Instrumental Quality Assessment for Speech Communication Systems

Users of speech communication systems expect a certain quality regarding the received speech signals. The so-called Quality of Experience (QoE) expresses to what extend the users’ quality expectations are met by a specific communication service and/or a service provider. The common numerical descriptor of the QoE is the Mean Opinion Score (MOS), which is, essentially, an averaged user rating obtained from a number of subjective listening experiments. The MOS scale ranges from 1 (bad) to 5 (excellent).

To circumvent the necessity for subjective listening experiments, which inconveniently require human test subjects, instrumental quality measures such as the Perceptual Evaluation of Speech Quality (PESQ) and the Perceptual Objective Listening Quality Assessment (POLQA) have been standardized by the ITU-T. These instrumental measures estimate the outcome (MOS) of subjective listening experiments by means of signal processing. While PESQ and POLQA offer a high correlation between subjective and objective MOS, they do not offer much information about the nature or cause of the perceived quality impairments.

The Technical Cause Analysis (P.TCA) work item of the ITU-T, however, provides a more differentiated evaluation scheme based on an (ideally) exhaustive list of audible signal impairments. The subjective annotation scheme asks test subjects to select impairments based on their prominence in the current degraded speech sample. Regarding steady-state noise impairments, available annotations include e.g. pink noise, white noise, hiss, and motorboating. Hence, this annotation scheme provides information about the nature, and to some extend even the cause, of the perceived impairments.

This research aims at the development of an instrumental quality measure which estimates the subjective annotations in accordance with the P.TCA scheme. Due to the assumed interdependence of the signal impairments and the root causes (e.g. packet loss, noise reduction, bandwidth restrictions, …) within a communication system, an additional estimator for the root causes is to be developed. Such an estimator may aid service providers with debugging and optimizing their networks and services towards an improved QoE.

Related topics:

  • speech analysis
  • speech quality
  • pattern recognition

Further interests:

  • adaptive filters
  • echo cancellation

Short CV

2017 - current   Research Assistant at Christian-Albrechts-Universität zu Kiel, Kiel, Germany
2016 - 2017   Academic Assistant at RWTH Aachen University, Germany
2015 - 2016   Internship at Sivantos GmbH in Erlangen, Germany
2014 - 2016   M.Sc. in Electrical Engineering, Information Technology, and Computer Engineering at RWTH Aachen University, Germany
2011 - 2014   B.Sc. in Electrical Engineering, Information Technology, and Computer Engineering at RWTH Aachen University, Germany


Internal PhD Students


Rasool Al-mafrachi
Christin Baasch
Analysis of Parkinson Speech
Christin Bald
Real-time Signal Processing for Magnetoelectric Sensors
Eric Elzenheimer
Medical Signal Processing
Marco Gimm
Tobias Hübschen
Instrumental Quality Assessment for Speech Communication Systems
Alexej Namenas
Cognitive-adaptive Target Detection and Tracking for SONAR Systems
Anton Namenas
Acoustic Environments and Evaluation of Communication Systems
Thorben Kaak
Real-time MIMO Signal Processing for Active SONAR Systems
Finn Spitz
Speech Analysis and Therapy for Parkinson Patients
Owe Wisch
Underwater Communication in Real-time MIMO-SONAR-Systems



Prof. Dr.-Ing. Gerhard Schmidt


Christian-Albrechts-Universität zu Kiel
Faculty of Engineering
Institute for Electrical Engineering and Information Engineering
Digital Signal Processing and System Theory

Kaiserstr. 2
24143 Kiel, Germany

Recent News

New PhDs in the DSS Team

Since January this year we have two new PhD students in the team: Elke Warmerdam and Finn Spitz.

Elke is from Amsterdam and she works in the neurology department in the university hospital in the group of Prof. Maetzler. Her research topic is movement analysis of patients with neurologic disorders. Elke cooperates with us in signal processing related aspects of her research. Elke plays ...

Read more ...