About the project
A measurement repository (DirPat) has been set up to archive all 3D and 2D directivity patterns measured at the Institute of Electronic Music and Acoustics, University of Music and Performing Arts in Graz. Directivity measurements have been made of various loudspeakers, microphones, and also of human speakers/singers for specific phonemes. The repository holds time domain impulse responses for each direction of the radiating or incident sound path. The data can be visualized with the provided 2D and 3D visualization scripts programmed in MATLAB. The repository is used for ongoing scientific research in the field of directivity evaluation of sources or receivers regarding localization, auditory perception, and room acoustic modeling. One goal of the project is to combine the visualization tools within the next updates and we explicitly support and recommend the SOFA file format. During the 144th AES Convention in Milan four contributions referring to the project have been presented.
144th AES Convention in Milan - Companion Contributions: E-Brief 425, 444, 447 and Paper 9977
The project DirPat is presented at the 144th AES Convention. The E-Brief is available at the AES website E-Brief 425. The E-Brief describes the purpose of the project and two of the commonly used measurement setups at IEM. Furthermore, the signal processing steps are described and exemplary measurement data is used to undermine the purpose of the tools.
The following proceedings and engineering briefs directly refer to balloon_holo:
Frank Schultz, Markus Zaunschirm, Franz Zotter (2018): “Directivity and Electro-Acoustic Measurements of the IKO”. In: Proceedings of 144th Audio Engineering Society, Milano, e-Brief #444. AES E-Library Link Download Poster
Nils Meyer-Kahlen, Franz Zotter, Katharina Pollack (2018): “Design and Measurement of a First-Order, Horizontally Beam-Controlling Loudspeaker Cube”. In: Proceedings of 144th Audio Engineering Society, Milano, e-Brief #447. AES E-Library Link
Thomas Deppisch, Nils Meyer-Kahlen, Franz Zotter, Matthias Frank (2018): “Surround with Depth on First-Order Beam-Controlling Loudspeakers”. In: Proceedings of 144th Audio Engineering Society, Milano, Paper #9977. AES E-Library Link
3D Visualization in MATLAB (simple viewer for single sources or receivers)
For visualization and analysis of the data that is stored in AES69 SOFA format (Spatially Oriented Format for Acoustics), directivity inspection tools developed in the last decade at IEM are also included in a Git repository. As for all tools that you may use for the visualization you need to install the sofa API (https://www.sofaconventions.org).
ballon_holo - Matlab GUI for Visualization
balloon_holo is a convenient open data visualization of acoustic transceivers, such as icosahedral (IKO) and cubical (CUBE) shaped loudspeaker arrays capable of 3rd order and 1st order Ambisonic beamforming, respectively. balloon_holo reads data in AES-69 SOFA and Matlab mat format of different transceivers (from IEM’s research interest history) and visualizes their directivities (far field radiation patterns) as
- 2D polar diagram
- 3D balloon
- directivity surface plot over frequency (sometimes called isobar plot)
for adjustable beam steering angle and frequency/frequency band.
The tool was initiated by Franz Zotter and is being currently maintained by Franz Zotter and Frank Schultz with additional contributions by Nils Meyer-Kahlen for cubical loudspeaker beamforming.
The figures below depict IEM’s IKO2 and exemplary balloon_holo renderings of IKO3 directivities.
2D Comparison Viewer in MATLAB
For visualization of 2D directivity data measured with the Double Circle Microphone Array (DCMA) a investigation tool has been developed. The viewer allows one to show the horizontal and vertical ring of the DCMA. Furthermore, it allows one to normalize onto the overall maximum of both patterns, or solely normalize each polar pattern on axis.
2D Continuous Polar Pattern Viewer and Spectrum Analyzer
Another visualization tool in the DirPat project is the Continuous Polar Pattern Viewer. It serves also as a player of the multichannel audio with the possibility to switch between audio channels and select a specific time instant in the recording. Therefore, a recording can be investigated within a quasi-realtime environment. Furthermore, the viewer allows one to analyze the spectrum of the current audio channel with a smoothing setting of the Fourier-coefficients 1/x octaves.
The repository offers source and receiver directivity data to download from the persistent data repository (phaidra.kug.ac.at) of the University of Music and Performing Arts, Graz.
Link to 3D Viewer (@git.iem): DirPat Viewer - 3D in MATLAB
Link to balloon_holo (IKO Viewer) balloon_holo Matlab Source Code
Link to 2D Comparison Viewer (@git.iem): DirPat Viewer - 2D Comparison Viewer in MATLAB
Link to 2D Polar Pattern Viewer and Spectrum Analyzer (@git.iem):
Phaidra Open Data Repository
Data is stored at the persistent archive phaidra.kug.ac.at of the University of Music and Performing Arts, Graz:
Link to repository (@phaidra): DirPat Database
- Sources (IKO and CUBE Loudspeakers)
IKO Filters & mcfx_convolver Config Files (tagged as May 2018 versions in git repo)
Gerriet K. Sharma (2016): “Composing with Sculptural Sound Phenomena in Computer Music”, Dr. art. dissertation, University of Music and Performing Arts Graz.
Setup of balloon_holo
- git clone of balloon_holo results in a folder and file structure as on left graphics
- download source/receivers’s specific Phaidra data (directivity measurements, beamforming filters) and copy into a dedicated folder as seen in right screenshot for IKO3 exemplarily
- start balloon_holo as main Matlab script
- makes sure that SOFA API is available and known in Matlab
- in balloon_holo GUI choose directory of transceiver to be analyzed in the selection box right top
- docu for parameters TBD