Paper: Comparing Approaches to the Spherical and Planar Single Layer Potentials for Interior Sound Field Synthesis

Feel free to download the presentation slides of our recent contribution Schultz, F.; Spors, S. (2014): “Comparing Approaches to the Spherical and Planar Single Layer Potentials for Interior Sound Field Synthesis.” In: Proc. of the EAA Joint Symposium on Auralization and Ambisonics 2014, Berlin. The paper is currently in the review process for an ACTA ACUST UNITED AC special issue on Auralization and Ambisonics. The article was successfully reviewed and will be supposedly published as Schultz, F; Spors, S. (2014):  “Comparing Approaches to the Spherical and Planar Single Layer Potentials for Interior Sound Field Synthesis.” In: Acta Acust united Ac, 100(6):900-911.

The authors plan to create a tutorial on analytic methods for sound field synthesis based on this manuscript, which can be accessed as a public BitBucket git repository under https://username@bitbucket.org/fs446/analytical_3d_sfs.git in near  future. Stay tuned.

The paper gives a compact recollection of analytic and explicit solutions for sound field synthesis using the single layer potential. It is shown that for planar and spherical secondary source distributions the same basic principles in solving the Fredholm integral equation within the spectral representation hold. The solutions are well introduced in literature known as Nearfield Compensated Higher Order Ambisonics (NFC-HOA) for spherical geometry and Spectral Division Method (SDM) for planar geometry. Taking the Helmholtz integral equation as starting point for solving the sound field synthesis problem, the equivalent sound-soft scattering approach leads to the same results. In the special case of a planar secondary source distribution the Neumann Green’s function incidentally leads to a single layer potential representation of the Helmholtz integral, which as the Rayleigh integral is an implicit and exact solution and was used for modern formulation of wave field synthesis.

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Maintenance Release of the SoundScape Renderer

This is mainly a bugfix release, but there are also a few minor new features:

  • The default number of threads is now obtained automatically.
  • Certain renderers are now available as Puredata externals. This is still quite experimental (a.k.a. buggy).
  • Minor GUI changes (no more “pie slices” on sources, larger fonts)

The new SSR release is available at http://spatialaudio.net/ssr/

SSR logo

Please feel free to post/send feedback for the SSR to

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Debian package available for the SoundScape Renderer

Due to the efforts of Johannes Zmölnig a debian package for the SoundScape Renderer (SSR) is now available. You can check out the details here.

openlogo-100

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Article: Sound Field Synthesis for Audio Presentation

The article Sound Field Synthesis for Audio Presentation from Jens Ahrens, Rudolf Rabenstein and Sascha Spors was published in the Spring 2014 issue of Acoustics Today.

AcousticsToday_fig4An overview on the application of loudspeaker arrays for audio presentation is given. The foundations of Wave Field Synthesis and Higher-Order Ambisonics are introduced in an intutive manner. The possibilites and applications of Sound Field Synthesis techniques in comparison with conventional methods like Stereophony are highlighted.

The article is enhanced online with animated versions of the figures.

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Paper: On the frequency response variation of sound field synthesis using linear arrays

Feel free to download the Slides and Paper for our recent contribution
Schultz, F.; Spors, S. (2014): “On the Frequency Response Variation of Sound Field Synthesis using Linear Arrays”. In Fortschritte der Akustik: Tagungsband d. 40. DAGA, Oldenburg.

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Paper: On Spatial-Aliasing-Free Sound Field Reproduction using Infinite Line Source Arrays

Please feel free to download the slides of our talk to the corresponding paper

Schultz, F.; Rettberg, T.; Spors, S. (2014): “On Spatial-Aliasing-Free Sound Field Reproduction using Infinite Line Source Arrays”. In Proc. of 136th Aud. Eng. Soc. Conv., Berlin. #9078.

Abstract:
Concert sound reinforcement systems aim at the reproduction of homogeneous sound fields over extended audiences for the whole audio bandwidth. For the last two decades this has been mostly approached by using so called line source arrays due to their superior abilities of producing homogeneous sound fields. Design and setup criteria for line source arrays were derived as Wavefront Sculpture Technology in literature. This paper introduces a viewpoint on the problem at hand by utilizing a signal processing model for sound field synthesis. It will be shown that the optimal radiation of a line source array can be considered as a special case of spatial-aliasing-free synthesis of a wave front that propagates perpendicular to the array. For high frequencies the so called waveguide operates as a spatial lowpass filter and therefore attenuates energy that otherwise would lead to spatial aliasing artifacts.

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Video: The BoomRoom: Mid-air Direct Interaction with Virtual Sound Sources

The BoomRoom: Mid-air Direct Interaction with Virtual Sound Sources from Jörg Müller, Matthias Geier, Christina Dicke and Sascha Spors is presented at the ACM CHI Conference on Human Factors in Computing Systems 2014.

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Paper: Perceptual Properties of Data-based Wave Field Synthesis

The paper “Perceptual Properties of Data-based Wave Field Synthesis” was presented by Sascha Spors and Hagen Wierstorf at the 40.Jahrestagung für Akustik (DAGA) in Oldenburg, Germany. DAGA2014_data_based_WFS

We investigated the capture of sound fields by spherical microphone arrays and their reproduction by Wave Field Synthesis. The limited number of microphones and loudspeakers, as well as other practical factors, impair the synthesized sound field. A special attention is drawn to the perceptual implications these impairments could have. In order to reproduce our findings you can take a look at the

 

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Sound Field Synthesis Toolbox 1.0.0 released

After a few years of work we finally are coming up with the 1.0.0 release of the Sound Field Synthesis Toolbox, which should be of great help for all simulations of sound field synthesis in Matlab/Octave.
You can download the latest release and you should have a look at the tutorial on github how to use it.

sfs-1.0.0

NEWS:
- added references for all driving functions
- streamlined nested conf settings; e.g. now it is no longer neccessary to set conf.ir.hcompfile if conf.usehcomp == false
- added WFS driving functions from Völk et al. and Verheijen et al.
- removed secondary_source_number() and xy_grid, because they are no longer needed
- enabled pre-equalization filter of WFS as default in SFS_config_example()
- fixed sound_field_mono_sdm_kx()
- Green's function for line sources returns now real values
- correct y-direction of plane waves for 3D NFC-HOA
- updated the test functions in the validation folder
- several small fixes

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Paper: Measurement of time-variant binaural room impulse responses for data-based synthesis of dynamic auditory scenes

The paper “Measurement of time-variant binaural room impulse responses for data-based synthesis of dynamic auditory scenes” was presented by Nara Hahn and Sascha Spors at the 40th Deutsche Jahrestagung für Akustik (DAGA) in Oldenburg.

The paper discusses a method and results for the measurement of time-varying binaural room impulse responses (BRIRs) of dynamic scenes. BRIRs are measured using so-called perfect sequences in combination with dynamic system identification methods.

The presentation slides as well as listening examples are available for download.

 

scenario_and_brirsScenario shown above: the direct path of the sound field emitted by the loudspeaker is disturbed by a moving person.

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