Wolfgang Kreuzer

  • Branched Tube Vocaltract Model


    Computational models for speech production and analysis have been of research interest since the 1960s. Most models assume the vocal tract (VT) to be a segmented straight tube, but when pronouncing  nasals like /m/ and /n/ or nasalized vowels the nasal part of the vocal tract plays an important part and a single tube model is not feasible anymore. Thus, it  is necessary to consider a branched tube model that includes an additional tube model for the nasal tract. For these branched models, the estimation of the cross section area of each segments from a given signal is highly non trivial and in general requires the solution of a non-linear system of equations.


    The problem is overdetermined, and we have to add additional restrictions to our solution, for example restrictions on upper and lower bounds of the area functions or smoothness assumption about the vocal tract. To that end we introduced e.g. probabilistic methods (variational Bayes) into our model estimation.

  • RailVib - Railway vibrations from tunnels


    Railway tunnels avoid direct acoustic annoyance by railway traffic. However, vibrations from tunnels propagate through the soil and lead to disturbances by percieved low frequency vibrations.

    The objective of this project is to develop and implement a mathematical model that takes a moving vibrating load into account. Furthermore, the surrounding soil is modeled as an anisotropic material, consisting of layers with arbitrary orientation.



    The propagation of the vibrations inside the tunnel are modelled by the finite element method (FEM), where the superstructure of the tunnel and the railway are considered. Vibrations outside the tunnel, propagating through the (infiinite) soil are modelled by the boundary element method (BEM). For a detailed model of the whole system, both methods have to be coupled.

  • Wavelets and Frames for space-time-frequency representation of acoustic wave fields

    The rapid increase in available computing power and the fast evolution of audio interfacing and transmission technologies have led to a new age of immersive audio systems to reproduce spatial sound with surrounding loudspeakers. Many of these approaches require a precise and robust space-time-frequency analysis of sound fields. The joint project of ARI and IRCAM  combines the mathematical concepts provided by the ARI with the profound knowledge in real-time signal processing and acoustics of IRCAM. It addresses fundamental research questions in both fields and aims at developing improved methods for the target applications mentioned above.

    The main questions that his project aims at are:

    • Is it possible to apply the frame-based signal-processing tools to a predefined geometrical alignment of microphones and/or loudspeakers (e.g. to the 64-channel spherical microphone array that is currently under development at IRCAM
    • How can acoustic fields on the sphere (e.g. measured with a spherical microphone array) be represented with frames in order to have better control of the space-time-frequency resolutions on different parts of the sphere?
    • Is it possible to apply this multi-resolution space-time-frequency representation to room acoustic sensing with multichannel spherical microphone arrays (e.g. to measure the spatial distribution of early reflections with higher resolution than provided with spherical harmonic analysis)?
  • Amadee: Frame Theory for Sound Processing and Acoustic Holophon

    S&T cooperation project 'Amadee' Austria-France 2013-14, "Frame Theory for Sound Processing and Acoustic Holophony", FR 16/2013

    Project Partner: The Institut de recherche et coordination acoustique/musique (IRCAM)

  • BIOTOP: Adaptive Wavelet and Frame techniques for acoustic BEM. FWF Project I-1018-N25

    Biotop Beschreibung
    Workflow Biotop


    Localization of sound sources plays an important role in our everyday lives. The shape of the human head, the torso and especially the shape of the outer ear (pinna) have a filtering effect on incoming sounds and thus play an important role for sound localization. This filtering effect can be described using the so called head related transfer functions (HRTFs). By calculating the distribution of the sound pressure around the head with numerical methods like the boundary element method (BEM), these HRTFs can be calculated numerically.


    In BIOTOP the numerical calculations shall be made more efficient by using adaptive wavelet- and frame techniques. Compared to commonly used BEM basis functions, wavelets have the advantage that wavelets can adapt better to a given distribution of the acoustic field on the head. As a generalization of wavelets, frames allow for an even more flexible construction method and thus for a better adaption to the problem at hand.

    BIOTOP combines abstract theoretical mathematics with numerical and applied mathematics. It is an international DACH (DFG-FWF-SFG) project between the Philipps-Universität Marburg (Stephan Dahlke), the University Basel (Helmut Harbrecht) and the ARI. The expertise of all three research groups shall be combined to develop new strategies and numerical methods. The project is funded by the FWF: Pr. Nr. I-1018-N25


  • Calm Tracks & Routes


    Upon first investigation, the design of new outward-curved noise barriers has an improved noise-shielding effect if absorbing material is applied. Further investigation shall prove this ability. Numeric simulations and measurements are being processed.


    Advanced boundary element methods (BEM) in two dimensions will prove the noise-shielding ability of the sound barrier. Different curvy and straight designs are compared to each other with respect to their shielding effect in the spectrum. Measurements at existing walls are processed and compared. Measurements are conducted without a noise barrier. A simulated softening affect of the noise barrier walls is used to simulate the noise signal behind the new barriers.


    Calma Tec has patented the designs and will offer new designs in practice.

    List of Deliverables:

    01. Traffic Noise Recording Plan. 02. Sound Data Storage, Retrieval and Spectrographic Description. 03. Descriptive Noise Statistics. 04. Pricipal Component Analysis. 05. Sound Barrier Mesh Models. 06. Simulation, Transfer Functions & Clustering. 07. Visualization. 08. Psychoacoustic Irrelevance. 09 Modulation Effects. 10. Subjective Preference Tests. 11. Conclusions

  • WiABahn - Acoustic Effect of Shielding Edges Near the Rail and Roofs Above Railway Platforms


    Railway platforms are located very close to the track and thus are assumed to alter the sound propagation. The degree of this effect, however, has not yet been investigated in detail


    The aim of the project WiaBahn was to investigate the shielding effect of railway platforms. One of the main questions was how to properly deal with the vicinity to the track, the platform’s large reflecting horizontal surface, and the often present canopy. It is unclear whether standard noise propagation prediction methods can be applied without modifications.


    Based on measurements directly at the platform as well as in the distance the acoustic effect of low railway platforms was investigated and suitable source models for the 2.5D boundary element method (BEM) as well as for standardized prediction methods were derived. The advantage of the 2.5D method which was also used in the project PASS is, that a constant cross-section can be combined with point sources or incoherent line sources which is not possible with pure 2D methods. 3D BEM is not feasible for such large structures.

    WiaBahn was funded by the FFG (project 845678) and the ÖBB. The project was done in cooperation with the  Austrian Institute of Technology (AIT, project leader) and Kirisits Engineering Consultants.