Conference PaperPDF Available

Authoring complex Ambisonic soundfields: An artist’s tips & tricks

Authors:

Abstract

When first working with Ambisonics, the artist is usually presented with encoding (panning) tools intended to spatialise single point sources. When complex soundfields are generated through this approach, the results may be regarded as created via a sound-scene based paradigm in some way modelling a real- world scene. In contrast, this paper presents a sound-kernel paradigm and techniques for the generation of complex soundfields. This approach instead focuses on the direct generation of complex soundfield kernels as a starting point. A number of spatial authoring approaches, ranging from time/spatial-domain to frequency/spatial-domain techniques, are presented, discussed and illustrated with sound examples—which include musical excerpts from the author’s catalogue. Strategies to ‘upgrade’ well known two-channel stereo effects to Ambisonics and soundfield kernel processing are also introduced. Additionally, spatial imagining transforms from the author’s Ambisonic ToolKit (ATK) are described and demonstrated, enabling the artist to control the generated complex soundfields. Keywords: ambisonics, surround sound, spatialisation, spatial filtering, digital audio effects
Sounds in SPACE Symposium
Friday, 17 June 2011
University of Derby
Derby, England
Joseph Anderson
independent artist
Authoring complex Ambisonic soundfields:
An artist’s tips & tricks
Joseph Anderson — 17 June 2011 Sounds in SPACE:Authoring Soundfields 2/11
Epiphanie Sequence
Kyai Pranaja (1998)
Mpingo (2003)
Pacific Slope (2002)
Composed in full 3D (periphonic) B-format
Using B-format source recordings
Published by Sargasso Records
UHJ Stereo on CD
B-format versions available (on request!)
Joseph Anderson — 17 June 2011 Sounds in SPACE:Authoring Soundfields 3/11
Ambisonic Encoding
OUTRS tetrahedral microphone array, courtesy Stephen Thornton
(www.michaelgerzonphotos.org.uk)
Soundfield microphone, courtesy Soundfield Ltd.
(soundfield.com)
Joseph Anderson — 17 June 2011 Sounds in SPACE:Authoring Soundfields 4/11
The Trick: A-format
Joseph Anderson — 17 June 2011 Sounds in SPACE:Authoring Soundfields 5/11
The Trick: Ambisonic Toolkit (ATK)
Networks
Audio Effects
Process in A-format!
Synthesis
… in A-format!
Joseph Anderson — 17 June 2011 Sounds in SPACE:Authoring Soundfields 6/11
ATK Imaging: Zoom
Zoom Transform
Dominance
Reshape Soundfield
Joseph Anderson — 17 June 2011 Sounds in SPACE:Authoring Soundfields 7/11
ATK Imaging: Focus
Focus Transform
Dominance
Related
Reshape Soundfield
Joseph Anderson — 17 June 2011 Sounds in SPACE:Authoring Soundfields 8/11
ATK Imaging: Push
Push Transform
Two metaphors:
Spatial Shelving-Filter
Re-align Tetrahedron
Reshape Soundfield
Joseph Anderson — 17 June 2011 Sounds in SPACE:Authoring Soundfields 9/11
Listening & Discussion
Ambisonic Toolkit
(SuperCollider Library)
Demonstration
Joseph Anderson — 17 June 2011 Sounds in SPACE:Authoring Soundfields 10/11
References
[1] J. Anderson, Epiphanie Sequence, vol. 28056. London: Sargasso, 2008.
[2] J. Anderson, “Introducing... The Ambisonic Toolkit,” in Proceedings of the Ambisonics Symposium 2009, Graz, 2009.
[3] J. Anderson and J. Parmenter, “The Ambisonic Toolkit,” Ambisonic Toolkit (ATK), 2011. [Online]. Available:
http://www.ambisonictoolkit.net/.
[4] J. L. Anderson, “Portfolio of Compositions,” PhD Thesis, University of Birmingham, 2003.
[5] C. Dodge and T. A. Jerse, Computer Music: Synthesis, Composition, and Performance. New York: Schirmer Books, 1985.
[6] K. Farrar, “Soundfi eld microphone: design and development of microphone and control unit,” Wireless World, pp. 48-50 (Oct.), 99-
103 (Nov.), 1979.
[7] R. Furse, “Sound System: Methods and systems for using transforms to modify the spatial characteristics of audio data,” U.S.
Patent GB 2467534 A11-Aug-2010.
[8] M. A. Gerzon, “Periphony: With-Height Sound Reproduction,” Journal of the Audio Engineering Society, vol. 21, no. 1, pp. 2-10,
Feb. 1973.
[9] M. A. Gerzon, Artifi cial Reverberation and Spreader Devices. NRDC, 1975.
[10] M. A. Gerzon, Panpot and Soundfi eld Controlls. NRDC, 1975.
[11] M. A. Gerzon, “Ambisonics in Multichannel Broadcasting and Video,” Journal of the Audio Engineering Society, vol. 33, no. 11, pp.
859-871, Nov. 1985.
[12] D. G. Malham and A. Myatt, “3-D Sound Spatialization using Ambisonic Techniques,” Computer Music Journal, vol. 19, no. 4, pp.
58-70, 1995.
[13] D. Menzies, “W-panning and O-format, tools for object spatialization,” in Proceedings of the Audio Engineering Society 22nd
International Conference on Virtual, Synthetic and Entertainment Audio, Espoo, Finland, 2002.
[14] SoundField Ltd., “SoundField Technology and B-Format,” SoundField: SoundField Technology and B Format, 2001. [Online].
Available: http://soundfi eld.com/soundfi eld/technology.php. [Accessed: 09-Jun-2011].
[15] S. Thornton, “Tetrahedral Recording Session Images,Michael Gerzon Audio Pioneer, 2009. [Online]. Available:
http://www.michaelgerzonphotos.org.uk/tetrahedral-recording-images.html. [Accessed: 17-Apr-2011].
[16] “Tetrahedron,” Tetrahedron - Wikipedia, the free encyclopedia, 11-May-2011. [Online]. Available:
http://en.wikipedia.org/wiki/Tetrahedron. [Accessed: 09-Jun-2011].
[17] “SuperCollider: real-time audio synthesis and algorithmic composition,” SuperCollider » About. [Online]. Available:
http://supercollider.sourceforge.net/. [Accessed: 15-Dec-2010].
Joseph Anderson — 17 June 2011 Sounds in SPACE:Authoring Soundfields 11/11
Thanks!!
josephlloydanderson@mac.com
www.ambisonictoolkit.net
... The encoded 2nd order ambisonic signal is converted to a 12-channel A-format signal and convolved with a B-format RIR which has been upsampled to 2nd order and converted to A-format impulse spectrum, a process that is performed automatically on first initialisation. A final step converts this reverberated A-format signal back to 2nd order B-format for decoding and audition (Anderson, 2011). ...
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Portfolio of Compositions
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Soundf i eld microphone: design and development of microphone and control unit Wireless World
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K. Farrar, " Soundf i eld microphone: design and development of microphone and control unit, " Wireless World, pp. 48-50 (Oct.), 99-103 (Nov.), 1979.