On the AES 59th Intl. Conference on Sound Reinforcement Engineering and Technology we presented the contribution
Straube et al. (2105): “Evaluation Strategies for the Optimization of Line Source Arrays.” In: Proc. of the 59th Audio Eng. Soc. Intl. Conf., Montreal, #2-1
Abstract: Line source arrays (LSAs) are used for large scale sound reinforcement, aiming at the synthesis of highly spatial aliasing-free sound fields for the whole audio bandwidth. Numerical optimization of the loudspeakers’ driving functions can considerably improve the homogeneity of the intended sound field. In this paper we propose enhanced visualization techniques characterizing the array performance. This may lead to a more convenient interpretation of the LSA radiation behavior. By additionally recommended technical quality measures the LSA design and the optimization requirements might be improved. The approach is exemplarily discussed for fictitious LSA models. Based on a least-mean-square error optimization using a loudspeaker weight energy constraint, the driving functions are derived. It is shown by means of the visualizations and measures why this optimization scheme being common practice in sound field synthesis applications is inappropriate for the problem at hand and that spatial aliasing has a large impact on the synthesized sound fields. We recommend to incorporate the proposed quality measures as criteria for future optimization approaches.
Feel free to download the presentation slides here.
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)
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.
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.
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.
- 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
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 Acoustics (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.
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.
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.
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.
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.
- 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