Three inverse problems in acoustics
Speaker: Dr. Nikolaos Stefanakis
Date: 18 February 2014 Time: 12:00-14:00
Location: "Alkiviades C. Payatakes" Seminar Room, FORTH, Heraklion, Crete
Host: Athanasios Mouchtaris


I will present selected topics from the three research projects that I have been involved in the past.

  1) Sound field reproduction in a room

The performance of a sound field reproduction system may be significantly degraded by the influence of the room, especially in cases where passive means are not a feasible option for treating the listening environment. In this case, active means are required. I am presenting two approaches based on optimal control for achieving room compensation. Simulation results demonstrate the effectiveness of each technique with respect to the acoustic conditions in the room.

2) Sparse underwater acoustic imaging

We exploit a natural sparsity prior in order to perform 3D underwater acoustic imaging using a newly built flexible-configuration sonar device. The computational challenges raised by the high-dimensionality of the problem are highlighted and we describe a strategy to overcome them. The proposed approach is used on real data acquired with the sonar to obtain an image of an underwater target.

3) Dynamical modeling of percussive instruments

The theory of nonlinear dynamical systems has opened new directions in the modeling and synthesis of natural sounds. I present an approach for modeling the nonlinear decaying behavior of percussive sounds in terms of a few first-order ordinary differential equations. Analysis – synthesis results presented for real recordings of a snare, a tom and a kick drum demonstrate the validity of the model.


Nikolaos Stefanakis received the Dr.-Ing. degree from the School of Electrical and Computer Engineering of National Technical University of Athens in 2008. In 2011 he was a post-doctoral researcher for the project “ECHANGE” in the research center of INRIA in Rennes, France. In 2012 and 2013 he was a post-doctoral researcher for the R&D project “DRUMBOX” in the University of Potsdam, Germany. Currently, he is a research fellow in the Institute of Computer Science at the Foundation for Research and Technology – Hellas. His research interests are in the fields of room acoustics, acoustic signal processing and music production.

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