Sound Field Synthesis Toolbox 2.2.1 released

Since our last announcement here at spatialaudio.net, two new releases of the Sound Field Synthesis Toolbox for Matlab/Octave have happend. The highlights of the new versions include a new online documentation at http://matlab.sfstoolbox.org and a new online theory documentation at http://sfstoolbox.org, which is directly linked in the corresponding code sections. Other big changes include a switch to the MIT license, more fractional delay methods, a new linear interpolation method for HRTFs and an update to the default WFS driving functions.

http://sfstoolbox.org

Download the SFS Toolbox 2.2.1 and have a look at the online documentation how to use it.

10.5281/zenodo.60606
Documentation Status

NEWS (2.2.1)

- fix delayoffset for FIR fractional delay filter
- add findconvexcone()
- simplify convolution()
- add linear interpolation working in the frequency domain
- fix pm option for delayline()

NEWS (2.2.0)

- fix impulse response interpolation for three points
- add the ability to apply modal weighting window to NFC-HOA in time domain
- change license to MIT
- update delayline() config settings
- add Lagrange and Thiran filters to delayline()
- replace wavread and warwrite by audioread and savewav
- convolution() excepts now two matrices as input
- allow headphone compensation filter to be a one- or two-channel wav file
- add new online doc at http://matlab.sfstoolbox.org/
- fix greens_function_mono() for plane wave and 3D
- replace conf.ir.useoriglength by conf.ir.hrirpredelay
- update default WFS driving functions
- add links to equations in online theory at http://sfstoolbox.org

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Digital Signal Processing – Lecture notes featuring computational examples

Digital signal processing is underlying many techniques for the processing of audio signals. The lecture notes to our masters course Digital Signal Processing are available as Open Educational Resource. The materials are provided in the form of jupyter notebooks featuring computation examples written in IPython 3. The materials can be inspected

The sources of the notebooks, as well as installation and usage instructions are available on GitHub. You can give the repository on GitHub a Star if you like the notebooks. You are invited to contribute by reporting errors and suggestions as issues or directly via Sascha.Spors@uni-rostock.de. I am also looking forward to ideas for new examples or topics.

10.5281/zenodo.59199

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Thesis: Sound Field Synthesis for Line Source Array Applications in Large-Scale Sound Reinforcement

The doctoral thesis
Frank Schultz (2016): “Sound Field Synthesis for Line Source Array Applications in Large-Scale Sound Reinforcement”, University of Rostock, URN: urn:nbn:de:gbv:28-diss2016-0078-1
was finally released.

Abstract: This thesis deals with optimized large-scale sound reinforcement for large audiences in large venues using line source arrays. Homogeneous audience coverage requires flat frequency responses for all listeners and an appropriate sound pressure level distribution. This is treated as a sound field synthesis problem rather than a directivity synthesis problem. For that the synthesis of a virtual source via the line source array allows for interpreting the problem as audience adapted wavefront shaping. This is either achieved by geometrical array curving, by electronic control of the loudspeakers or by ideally combining both approaches. Obviously the obtained results depend on how accurately an array can emanate the desired wavefront. For practical array designs and setups this is affected by the deployed loudspeakers and their arrangement, its electronic control and potential spatial aliasing occurrence. The influence of these parameters is discussed with the aid of array signal processing revisiting the so called wavefront sculpture technology and proposing so called wave field synthesis as a suitable control method.4217367580-SPLxy_Slides_Teaser

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Release 0.3.1 of the Sound Field Synthesis Toolbox for Python

We are pround to announce release 0.3.1 of the Sound Field Synthesis Toolbox for Python.

This release features

  • Calculation of the sound field scattered by an edge
  • Various driving functions for sound field synthesis using an edge-shaped secondary source distribution
  • Several refactorings, bugfixes and other improvements

The Python port of the Sound Field Synthesis Toolbox features the calculation of the synthesized sound field for various sound reproduction methods for the monofrequent case. Functionality for visualization of sound fields, as well as a set of auxiliary functions is included. The documentation provides installation instructions, usage examples and details on the API.

diffraction_edge

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Paper: On Analytic Methods for 2.5-D Local Sound Field Synthesis Using Circular Distributions of Secondary Sources

In the IEEE/ACM Transactions on Audio, Speech, and Language Processing  (Volume:24 ,  Issue: 5 ) we published

Winter, F.; Ahrens, J.; Spors, S. (2016), “On Analytic Methods for 2.5-D Local Sound Field Synthesis Using Circular Distributions of Secondary Sources,” In: IEEE/ACM Transactions on Audio, Speech, and Language Processing, vol. 24, no. 5

The paper can be found here.

Abstract:
Sound Field Synthesis techniques reproduce a virtual sound field inside an
extended listening area using a distribution of loudspeakers located on the
area’s boundary. The theoretical foundations of such techniques assume a
spatially smooth boundary. Non-smooth shapes, like e.g. rectangles, are however
more suitable in practical applications since the loudspeaker setup has to
fit into the architecture of the listening room. Such discrepancy introduces
diffraction artefacts to the reproduced sound field. Consequentially, deviations
from desired sound field with respect to amplitude and spectral properties
are present.
This paper compares Wave Field Synthesis, Local Wave Field Synthesis, and an
analytically derived solution for rectangular geometries regarding the
mentioned artefacts.

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Paper: A Comparison of Sound Field Synthesis Techniques for Non-Smooth Secondary Source Distributions

On the 42nd DAGA conference we presented the contribution

Winter, F.; Spors, S. (2016): “A Comparison of Sound Field Synthesis Techniques for Non-Smooth Secondary Source Distributions.” In: Proc. of
42nd DAGA, Aachen.

Local Wave Field Synthesis for Rectangular Arrays

Abstract:
Sound Field Synthesis techniques reproduce a virtual sound field inside an
extended listening area using a distribution of loudspeakers located on the
area’s boundary. The theoretical foundations of such techniques assume a
spatially smooth boundary. Non-smooth shapes, like e.g. rectangles, are however
more suitable in practical applications since the loudspeaker setup has to
fit into the architecture of the listening room. Such discrepancy introduces
diffraction artefacts to the reproduced sound field. Consequentially, deviations
from desired sound field with respect to amplitude and spectral properties
are present.
This paper compares Wave Field Synthesis, Local Wave Field Synthesis, and an
analytically derived solution for rectangular geometries regarding the
mentioned artefacts.

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Paper: On the Connections of Wave Field Synthesis and Spectral Division Method Plane Wave Driving Functions

On the 42nd DAGA conference we presented the contribution

Schultz, F.; Spors, S. (2016): “On the Connections of Wave Field Synthesis
and Spectral Division Method Plane Wave Driving Functions.” In: Proc. of
42nd DAGA, Aachen.
Please feel free to download the slides.

Abstract:
Wave Field Synthesis (WFS) is a well-established sound field synthesis (SFS) technique that uses a dense spatial distribution of loudspeakers arranged around an extended listening area. It has been shown that WFS based on the Neumann Rayleigh integral constitutes the high-frequency and/or farfield approximation of the explicit SFS solution, such as the Spectral Division Method (SDM) and Nearfield Compensated Higher-Order Ambisonics (NFC-HOA). However, for SFS of a virtual plane wave using a linear loudspeaker array a supposed mismatch between the SDM and a WFS driving function has been reported in literature.
In this paper we will derive the WFS plane wave driving functions using the same stationary phase approximation approach as introduced for the virtual non-focused point source. This yields WFS driving functions either for a reference point or for a parallel reference line. It is shown that the latter is identical with the high-frequency and/or farfield approximated SDM solution. Thus, with no mismatch existing, the SFS fundamentals are proven to be consistent.

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Release of Two!Ears Auditory Model Version 1.2

A new release of the Two!Ears auditory model is available

10.5281/zenodo.47487You can download the release on the Two!Ears website. Check out the installation guide.

Besides lots of bug fixes, this release features:
Blackboard system:
* Replaced GmtkLocationKS by GmmLocationKS
* Remove dependency on external GMTK framework
New Examples:
* GMM-based localisation under reverberant conditions

 

TWO!EARS is a project funded by the Seventh Framework Programme (FP7) of the European Commission, as part of the Future Emerging Technologies Open Programme “Challenging current thinking” (call FP7-ICT-2013-C).

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Sound Field Synthesis Toolbox 2.1.0 released

A new release of the Sound Field Synthesis Toolbox for Matlab/Octave is available. The highlights of the new version include several improvements for time-domain NFC-HOA simulations, new virtual line sources for WFS and NFC-HOA, and the ability to set t=0 for time-domain simulations to the start of the virtual source.

sfs_v2.1.0

Download the SFS Toolbox 2.1.0, PDF documentation and have a look at the tutorial on github how to use it.

10.5281/zenodo.47292

NEWS:

- make conf struct mandatory
- add new start message
- fix handling of 0 in least squares fractional delays
- fix NFC-HOA order for even loudspeaker numbers to N/2-1
- add conf.wfs.hpreFIRorder as new config option (was hard coded to 128
before)
- speed up secondary source selection for WFS
- rename chromajs colormap to yellowred
- fix tapering_window() for non-continuous secondary sources
- remove cubehelix colormap as it is part of Octave
- add conf.wfs.t0 option with is useful, if you have more than one
virtual source
- virtual line sources are now available for monochromatic WFS and NFC-HOA
- allow arbritrary orders for time-domain NFC-HOA simulations

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Online Exercises for Communication Acoustics

The exercises to our course “Communication Acoustics” are available online:

Communication Acoustics Exercises

For most exercises, we are using the programming language Python within Jupyter notebooks.

You can read a static online version of the exercises using the link above, you can get all the notebooks and additional files from the Github repository and run them on your computer with Jupyter, or you can run them interactively in your browser by clicking on Binder right now!

If you find errors or have suggestions for improvements, please open an issue on Github (you’ll need to create a Github account first) or leave a comment right here.

Have fun!

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