The Year 2024 in Review

 

Speech and Audio News

The audio team has not changed in terms of members. For Karolin Krüger, 2024 was characterized by the two collaborations initiated in 2023. In terms of auditory feedback modulation, i.e. changing one's own voice in real time in the sense of hoarseness and playing it back through headphones, the first study to investigate the effect was analyzed during the course of the year. The most effective approach to adding noise (noise in the sense of unvoiced signal components) was identified as part of a linear prediction, which was then to be further analyzed in a second phase of the study in terms of the intensity of the noise and the investigation of an aftereffect. For this purpose, Karolin implemented new functions and the new modes for the procedure. During the evaluation of this part of the study, a compensatory reaction to the auditory change was observed in healthy subjects, so we are eagerly awaiting the results with pathological speakers. Furthermore, in collaboration with two master's theses, we also worked on improving the effect in terms of naturalness. We first implemented a signal processing-based approach that includes more speech domains that influence hoarseness. Since such a system has a number of parameters that are difficult to parameterize, a second master's thesis was also started at the end of the year to investigate the change in the voice in terms of hoarseness using machine learning.

In the project with the UKSH, a precise test procedure was developed and implemented over the course of the year, so that tremors can now be recorded using accelerometers and EMG sensors, as well as video data, in parallel with the voice recordings. The comprehensive test was carried out in a series of tests at the TF with many members. Subsequently, some adjustments were made, but we can also add the data to the resulting database, as the extraction of updated features for the overall data set was also an adjustment as part of this preparation. At the end of the year, the first test recording was then carried out at UKSH to test the premises and conditions. In 2025, it will therefore be possible to start building the database of patients straight away.

 

Medical News

Moritz has been a member of the chair and in CRC 1261 since mid-2023. To this end, he put a lot of effort into the preparation and ultimately the successful execution of the CRC defense at the beginning of last year. Overall, the project (B2), which has now been extended for the third funding period, focuses on the magnetic localization of medical devices. The main subjects are ultrasound probes with magnetic sensors and a capsule with an integrated magnetic actuator for analyzing gastrointestinal function.

Over the past year, Moritz has primarily worked on preliminary tasks for this project. Using a self-built setup consisting of three nested Helmholtz coils, he generated a directed magnetic field. Through algorithmic evaluation of the excitation signals and sensor data in real time, he estimated the sensor characteristics. A nested control approach is used in this process, as the field direction must be changed when certain criteria are met, while at the same time, the step size of the underlying NLMS algorithm is adaptively adjusted. The result is an estimation of the sensor behavior dependent on direction and frequency, achieved with comparatively low temporal and measurement effort, which then incorporates the necessary modeling and assumptions for localization tasks. The improvement, expansion, and evaluation of this approach were significantly advanced over the course of the year and also documented in a journal publication. Furthermore, Moritz has helped with the start of the design of a new hardware setup for the localization tasks, identifying the necessary components, and planning the connections between the system components.

Patricia ....

Tobias ...

Over the past year, Erik has focused intensively on various projects related to non-invasive electroanatomical mapping. A significant milestone was the publication of our paper "Enhancing Non-invasive Electroanatomical Mapping with Dynamic Sensor Arrays" at the IEEE Sensors Conference, which he presented in October in Kobe, Japan. Johannes also attended the conference, and together they visited the SPRing-8 particle accelerator and Gentiane Venture's GVLab, which provided valuable insights for our research.

In the fall, Erik participated in the Computing in Cardiology (CIC) conference in Karlsruhe, where he presented a poster on all-pass filters in heart models. The positive feedback and scientific exchange brought important impulses for his work on optimizing propagation velocities in cardiac models.

This research topic has evolved into a central component of his work and resulted in a comprehensive journal paper titled "Gradient-based Optimization of All-pass Filter Networks for Non-invasive Electroanatomical Mapping," which is about to be submitted. Erik has also continued his theoretical work on the state-space model for estimating myocardial current densities, laying important groundwork for future clinical applications of our approach.

Johannes has been working on the magnetic analysis of human movement at the chair since summer 2020 as part of the Collaborative Research Center 1261. For the last year, he was mostly focused on the practical application of ME sensors in movement analysis. With the system established the year before, Johannes was now able to conduct larger scale gait experiments. He set up a system of four triaxial ME sensor arrays and two triaxial coils to measure distances between the participants lower limbs and to a fixed infrastructure. To overcome some of the limitations of the system (equalizing inaccuracies, sensor tilt), he conceptualized a system-level calibration scheme based on the optical reference system. With a gradient-descent approach, a correction matrix was optimized to minimize the error between the magnetic distance estimation and the reference for each actuator-sensor pair. With this method, an accuracy in terms of the mean absolute error of below 1 cm during gait measurements was achieved. An overview on the system and the calibration were published as “A magnetoelectric distance estimation system for relative human motion tracking”.

Johannes also presented adjacent topics such as “Proof of principle: Full 6D point-to-point motion tracking with magnetoelectric sensors” at “IEEE Sensors 2024” in Kobe, Japan and “ME cantilever sensors: From magnetic motion tracking to human gait analysis” at the “Workshop on Precision Sensing” at University of Minnesota.

 

SONAR News

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Outreach

Since Tobias is now responsible for our outreach activities in terms of school outreach, a lot of events took place. Tobias visited several school classes and explains what electrical engineering means and did several demos for the school students. In addition, the so-called "open lab day" at the faculty of engineering is now an established event that takes place a few days before the school summer holydays start. Details about these events can be found on a special website.

 

Some Numbers

  • This year the number of publications was a bit larger compared to 2022 - we published five journal papers, eleven conference papers, and three book chapters.

  • Comparted to 2022 we were agian able (as last year) to increase  the number of bachelor and master theses. 14 theses were started in 2023: two bachelor theses and 12 master theses.

  • In terms of doctoral degrees we "extended the name" of two people: Robbin Romijnders and Arthur Wolf sucessfully defended their research in 2023. Congratulations to both of them.

 

Our "GaS Club"

The "Gesellschaft für angewandte Signalverarbeitung" (GAS) currently have 43 supporting members and two companies.

The society annually awards the best thesis in the field of digital signal processing and system theory. Particular attention is paid to scientific and technical claim and the practical relevance of the work. The complete DSS-Group evaluates the student’s commitment, their ability to work multidisciplinary and in a team. This year Michael Hochmuth received the award for his master thesis “Realtime Improvement of Audio Signals in Underwater Communication”. In addition, Mr. Hochmuth was able to present the results of his work at the DAGA (annual conference for acoustics) and exchange ideas with interested parties and other researchers.

 

Some Pictures from 2024

 
Looking at the Baltic Sea ...   Finn Röhrdanz - one of the new doctoral researchers in the group ...
     
 
Group picture during our DSS Sylt retreat ...   Karoline Gussow -also new in the DSS team ...
     
 
Patricia and Petra - enjoying a long walk on the beach ...   Karoline and Kosta while doing underwater ship recordings ...