Paper: On Fractional Delay Interpolation for Local Wave Field Synthesis

On the 24th European Signal Processing Conference (EUSIPCO) conference we presented the contribution

Winter, F.; Spors, S. (2016): “On Fractional Delay Interpolation for Local Wave Field Synthesis.” In: Proc. of the 24th European Signal Processing Conference (EUSIPCO), 2016.

Additional Material can be found here.

tmp

Abstract:
Wave Field Synthesis aims at the accurate reproduction of a sound field inside an extended listening area which is surrounded by individually driven loudspeakers. Recently a Local Wave Field Synthesis technique has been published which utilizes focused sources as a distribution of virtual loudspeakers in order to increase the reproduction accuracy in a particular local region. Similar to conventional Wave Field Synthesis, this technique relies heavily on delaying and weighting the input signals of the virtual sound sources. As these delays are in general not an integer multiple of the input signals’ sample rate, delay interpolation is necessary. This paper analyses in how far the accuracy of the delay interpolation influences the spectral properties of the synthesised sound field. The results show, that an upsampling of the virtual source’s input signal is an computationally efficient tool which leads to a significant increase of accuracy.

Posted in Papers | Tagged , , | Leave a comment

Paper: Improved Driving Functions for Rectangular Loudspeaker Arrays Driven by Sound Field Synthesis

The paper Improved Driving Functions for Rectangular Loudspeaker Arrays Driven by Sound Field Synthesis by Sascha Spors, Frank Schultz and Till Rettbergs derives improved driving functions for rectangular loudspeaker arrays by applying the equivalent scattering approach. The following supplementary data has been published together with the paper:

edge_esa

Posted in Papers, Reproducible Research | Tagged , , | Leave a comment

Release of Two!Ears Auditory Model Version 1.3

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

10.5281/zenodo.61790You can download the release on the Two!Ears website. Check out the installation guide.

This release fixes mainly bugs and adds the following two new features:
Blackboard system:
* Improve DnnLocationKS to better predict location for synthesized sound fields
New Dataset:
* Results from a paired-comparison test investigating listening preference for WFS and stereo

 

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).

Posted in Announcement, Reproducible Research | Tagged , , | Leave a comment

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

Posted in Announcement, MATLAB, Reproducible Research | Tagged | Leave a comment

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

Posted in Open Educational Resource | Tagged , , , | Leave a comment

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

Posted in Publications | Leave a comment

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

Posted in Announcement, Reproducible Research | Tagged , , , | Leave a comment

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.

Posted in Papers, Publications | Tagged , , | Leave a comment

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.

Posted in Announcement | Leave a comment

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.

Posted in Papers | Leave a comment