SOFA: Spatially Oriented Format for Acoustics

The spatially oriented format for acoustics (SOFA) is dedicated to store all kinds of acoustic information related to a specified geometrical setup. SOFA can describe simple HRTF measurements, but it also can store measurements of something fancy like SRIRs recorded with a 64-channel microphone array in a multi-source excitation situation or directivities of a loudspeaker. SOFA is easily extendable, highly portable, self-describing, and numerically efficient.

SOFA defines the structure of data and metadata in the so-called conventions. All data is stored in the numerical container netCDF. The data description is an extendable description, with simple conventions for free-field HRTFs and more complex conventions for microphone-array measurements in reverberant spaces even when excited by a loudspeaker array. We use global geometry description related to the room and local geometry description related to the listener and source, without limiting the number of acoustic transmitters and receivers. Room descriptions can be attached by linking a CAD file to a SOFA file. Networking support is provided enabling partial access of data from client computers.

SOFA is a standard of the Audio Engineering Society available as AES69. It has been standardized in 2015, re-affirmed in 2020, and updated in 2022, with the lates standard version representing SOFA 2.1. 

Development

SOFA development is coordinated by Piotr Majdak, but SOFA and SOFA-related tools are developed by many contributors worldwide: 

  • SOFA 1.0 (AES69-2015): Piotr Majdak, Markus Noisternig, Matthieu Parmentier, Harald Ziegelwanger, Thibaut Carpentier, Yukio Iwaya, Rozenn Nicol, Agnieszka Roginska, Yôiti Suzuki, Kanji Watanabe, and Hagen Wierstorf, as well as C. Pike, T. Sporer, T. Ammermann, S. Bharitkar, W. De Bruijn, M. Emerit, F. Fleischmann, K. Hamasaki, A. Harma, J-M. Jot, M. Kelly, R. Kessler, T. Knowles, F. Melchior, B. Olson, G. Pallone, C. Par, A. Pereira, J. Plogsties, E. Ronciere, B. van Daele, W. Woszczyk, F. Camerer.
  • SOFA API (2015-2021): Piotr Majdak, Michael Mihocic, Harald Ziegelwanger, Hagen Wierstorf, Wolfgang Hrauda, Fabian Brinkmann, and Felix Perfler.
  • libmysofa (since 2016): Christian Hoene and Piotr Majdak.
  • SOFA 2.0 (AES69-2020): Piotr Majdak, Markus Noisternig, Julian De Muynke, Franz Zotter, and Fabian Brinkmann, as well as Jens Ahrens, S. Norcross, C. Pike, A. Farina, L. Neumann.
  • SOFA Toolbox (since 2022, succeeding SOFA API): Piotr Majdak, and Michael Mihocic.
  • SOFA 2.1 (AES69-2022): Piotr Majdak, Markus Noisternig, Julian De Muynke, Franz Zotter, Fabian Brinkmann, Michael Mihocic, and David Ackerman, as well as J. Ahrens, S. Norcross, C. Pike, A. Farina, L. Neumann.

Since 2020, the file extension .sofa is associated with SOFA files by IANA. 

In 2013, SOFA has been awarded with the Reproducible Research Prize by the Centre for Digital Music at Queen Mary, University of London. 

More SOFA-related resources can be found at www.sofaconventions.org.

SOFA-related subprojects at ARI

SOFA Toolbox

Team: Piotr Majdak and Michael Mihocic. 

Development of the reference software toolbox for handling SOFA files in Matlab and Octave. Open-source software free available under the EUPL v1.2. The releases are provided at Sourceforge. The sources are stored at github.

Database repository

Team: Piotr Majdak and Michael Mihocic. 

Maintainence of a Mediawiki collecting SOFA-related information such as SOFA Conventions, SOFA datasets and files, as well as software and toolboxes. Link: https://www.sofaconventions.org/. 

Measurement of Head-Related Transfer Functions

Team: Michael Mihocic and Piotr Majdak.

Long-term subproject to measure HRTFs at ARI, see the project page. 

NERO

Team: Pedro Lladó (University of Surrey), Katharina Pollack, Nils Meyer-Kahlen (Aalto University), and Piotr Majdak.

Subproject aiming at creating an optimal HRTF set. Currently under development, see this teaser.

HRTF Normalization

Team: Hélène Bahu (IRCAM), Rapolas Daugintis (Imperial London), Piotr Majdak, Markus Noisternig (IRCAM), Thibaut Carpentier (IRCAM), Agnieszka Roginska (New York University), Areti Andreopoulou (University of Athens), Jean-Marc Jot (Virtuel Works), Kaushik Sunder (Embody), Michael Mihocic, et al. 

This subproject aims at defining processes to normalize HRTF representations such that HRTFs of the same listener are not affected by the measurement locaation, equipment, nor post-processing methods. See this public discussion. Currently under development. 

SOFA-Related Publications

  1. Majdak, P., Zotter, F., Brinkmann, F., De Muynke, J., Mihocic, M., and Noisternig, M. (2022). “Spatially Oriented Format for Acoustics 2.1: Introduction and Recent Advances,” J Audio Eng Soc 70, 565-584. DOI: 10.17743/jaes.2022.0026.
  2. Mihocic, M., Majdak, P., Zotter, F., Brinkmann, F., De Muynke, J. et al (2023). “Recent Advances in the Spatially Oriented Format for Acoustics (SOFA, AES69),” in the proceedings of the 10th Forum Acusticum, Turin, Italy. 
  3. Majdak, P., Mihocic, M., Zotter, F., Brinkmann, F., De Muynke, J., and Noisternig, M. (2023). “Spatially Oriented Format for Acoustics 2.1: Introduction and Recent Advances,” presented at the 154th Convention of the Audio Engineering Society (AES), Aalto, Finland.
  4. Mihocic, M., Majdak, P., Noisternig, M., Brinkmann F., Zotter F., De Muynke, J. (2022). “Representing Directivities by Means of the Spatially Oriented Format for Acoustics (SOFA),” presented at the Vienna Talk, Vienna.
  5. Majdak, P., Mihocic, M., Noisternig, M., Brinkmann F., Zotter F., De Muynke, J. (2022). “Storing Head-Related Transfer Functions in the Spatially Oriented Format for Acoustics,” presented at the symposium All Around Audio, St. Pölten, Austria.
  6. Iwaya, Y., Watanabe, K., Majdak, P., Noisternig, M., Suzuki, Y., Sakamato, S., Takane, S., Sato, S. (2014). "Spatially Oriented Format for Acoustics (SOFA) for Exchange Data of Head-related Transfer Functions," technical report for the Institute of Electronics, Information and Communication Engineers (IEICE).
  7. Majdak, P., Carpentier, T., Nicol, R., Roginska, A., Suzuki, Y., Watanabe, K., Wierstorf, H., Ziegelwanger, H., and Noisternig, M. (2013). "Spatially oriented format for acoustics: a data exchange format representing head-related transfer functions," in proceedings of the 134th Convention of the Audio Engineering Society (AES), Roma, Italy, Convention Paper 8880.
Hearing

Team