Tutorial: Foundations and Practical Aspects of Sound Field Synthesis

Sascha Spors and Franz Zotter gave a tutorial on the foundations and practical aspects of sound field synthesis at the 138th Convention of the Audio Engineering Society. The slides of the tutorial can be downloaded under the DOI: 10.13140/RG.2.1.1025.5527.

AESsoundfigure03

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Paper: Physical Properties of Local Wave Field Synthesis Using Circular Loudspeaker Arrays

At the 10th European Congress and Exposition on Noise Control Engineering (EuroNoise) we presented the contribution
Winter, F.; Spors, S. : “Physical Properties of Local Wave Field Synthesis Using Circular Loudspeaker Arrays”. In: Proc. of the 10th European Congress and Exposition on Noise Control Engineering (EuroNoise)

Winter_2015_Aliasing_Local_Wave_Field_Synthesis_Circular

The reproduction accuracy of sound field synthesis techniques, like e.g. Wave Field Synthesis (WFS) or near field compensated Higher-Order Ambisonics, is limited due to practical aspects. For the audible frequency range the desired sound field can not be synthesized aliasing-free over an extended listening area, which is surrounded by a discrete ensemble of individually driven loudspeakers. However, it is suitable for certain applications to increase reproduction accuracy inside a smaller (local) listening region while stronger artifacts outside are permitted. A local Wave Field Synthesis method utilizes focused sources as a distribution of virtual loudspeakers which are placed more densely around the local listening area. These virtual loudspeakers are then driven by conventional WFS techniques. This paper establishes an analytical framework to analyze the physical properties of local WFS for circular loudspeaker arrays.

The presentation slides can be found here.

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Two!Ears Summer School on Active Machine Hearing

Two!Ears Summer School on Active Machine Hearing (Two!Ears’2015)
September 21-25, 2015  –  LAAS-CNRS (Europe Room), Toulouse, France.

The aim of this Summer School is to provide a comprehensive training in active machine hearing.  A review of sound perception and analysis, as well as advanced topics, will be presented.  The training will end with a challenge: the delegates will be put into teams, each of which be provided a simplified robotic platform endowed with a binaural sensor; the aim will be to integrate the many functions studied during the 3.5 days of the training so as to enable this robotic platform to analyze dynamic auditory scenes in a small-scale environment.

Visit the website http://twoears2015.sciencesconf.org, and be prepared for a wonderful experience in Toulouse! Online registration will be shortly available.  An RSS feed is also available so as to keep up to date.

Two!Ears (12.2013—11.2016) has been funded by the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement nº618075, see http://www.twoears.eu.

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Sound Field Synthesis Toolbox 1.2.0 released

A new release of the Sound Field Synthesis Toolbox for Matlab/Octave is available. This will be the last release without SOFA support, so the main concern was bug fixing. Beside that the other highlight is the inclusion of a new PDF documentation that provides a mathematical treatment of the underlying theory and derives all the driving functions used in the Toolbox.

Download the SFS Toolbox, PDF documentation and have a look at the tutorial on github how to use it.

sfs-doc

NEWS:

- add PDF documentation "Theory of Sound Field Synthesis"
- fix remaining usegnuplot config entry
- change default dB color map to chromajs
- add missing hgls2 functionality (fractional delays)
- add cubehelix and chromajs color maps
- remove noise() function, use the one from the LTFAT Toolbox instead

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Free database of single-channel and binaural room impulse responses of a 64-channel loudspeaker array for different room configurations

At the 138th AES Convention in Warsaw, we presented the freely available database of single-channel and binaural room impulse responses (RIRs and BRIRs) measured in our rectangular 64-channel loudspeaker array at the University of Rostock under varying room acoustical conditions. The RIRs have been measured at three receiver positions for four different absorber configurations. Corresponding BRIRs for head-orientations in the range of ±80° in 2° steps with a KEMAR manikin have been captured for a subset of seven combinations of position and absorber configurations. The data is provided in the Spatially Oriented Format for AKEMARcoustics (SOFA) standardised in AES69 standard for file exchange. The database can be used to study the influence of the listening room on multichannel audio reproduction.

You can find the database here. The poster of the AES Convention can be downloaded here.

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Paper: Physical Properties of Local Wave Field Synthesis Using Linear Loudspeaker Arrays

At the 138th AES convention we presented the contribution
Winter, F.; Spors, S. : “Physical Properties of Local Wave Field Synthesis Using Linear Loudspeaker Arrays“. In: Proc. of the 138th Audio Eng. Soc. Convention, Warsaw, #9321.

Wave Field Synthesis aims at a physically accurate synthesis of a desired sound field inside an extended listening area. Due to limitations of practical loudspeaker setups, the accuracy of this sound field synthesis technique over the entire listening area is limited. Local Wave Field Synthesis narrows the spatial extent down to a local listening area in order to improve the reproduction accuracy inside this limited region. Recently an method has been published, which utilizes focused sources as a distribution of more densely placed virtual secondary sources around the local area. Within this paper, an analytical framework is established to analyze the physical properties of this approach for linear loudspeaker setups.

The presentation slides can be found here.

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Paper: Discussion of the Wavefront Sculpture Technology criteria for straight line arrays


At the upcoming 138th AES convention we will present the paper

Schultz, F.; Straube, F.; Spors, S. (2015): “Discussion of the Wavefront Sculpture Technology criteria for straight line arrays.” In: Proc. of the 138th Audio Eng. Soc. Convention, Warsaw, #9323.
Abstract:
Wavefront Sculpture Technology introduced line source arrays for large scale sound reinforcement, aiming at the synthesis of highly spatial-aliasing free sound fields for full audio bandwidth. The paper revisits this technology and its criteria for straight arrays using a signal processing model from sound field synthesis. Since the latest array designs exhibit very small driver distances, the sampling condition for grating lobe free electronic beam forming regains special interest. Furthermore, a discussion that extends the initial derivations of the spatial lowpass characteristics of circular and line pistons and line pistons with wavefront curvature applied in subarrays is given.

I’ve managed to compile a pre-release, stand-alone readable version of the 4th chapter from my intended PhD-thesis, that covers the topics discussed in the paper. Feel free to download this draft. This rather long treatment revisits the WST technology from a different viewpoint than initially given in the original literature. The content of the mentioned contribution can be found in Sec. 1.5.
The slides of the talk can be downloaded here.

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Sound Field Synthesis Toolbox 1.1.0 released

A new release of the Sound Field Synthesis Toolbox for Matlab/Octave is available. Beside some important bug fixes it introduces local WFS as a new synthesis method as one of its highlights.
You can download the latest release and you should have a look at the tutorial on github how to use it.

sound_field_localwfs_2d

NEWS:
- fix amplitude bug in get_ir() and ir_generic()
- remove direct gnuplot plotting
- add support for local Wave Field Synthesis
- the length of the dirac impulse response is now an option for dummy_irs()
- fix iseven(), isodd() for very large numbers
- correct the sign for Wave Field Synthesis driving functions

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Paper: Parameter Analysis for Range Extrapolation of Head-Related Transfer Functions using Virtual Local Wave Field Synthesis

Winter_2015_HRTF_Extrapolation_Local_WFS_exampleAt the 41st German Annual Conference on Acoustics (DAGA) we presented the contribution
Winter, F.; Spors, S. : “Parameter Analysis for Range Extrapolation of Head-Related Transfer Functions using Virtual Local Wave Field Synthesis”. In Proc. of the 41. Jahrestagung für Akustik, Nürnberg.

The presentation slides can be found here.

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Paper: On the Connections between Radiation Synthesis and Sound Field Synthesis using Linear Arrays

On DAGA  41st we will present the contribution
Schultz, F.; Spors, S. (2015): “On the Connections between Radiation Synthesis and Sound Field Synthesis using Linear Arrays”. In: Proc. of the 41. Jahrestagung für Akustik, Nürnberg.

Please feel free to download the presentation slides and the paper.

SFSModel

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