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Ambisonics & the ATK @ DXARTS

  • November 2017
DOI:10.13140/RG.2.2.18161.38242
  • Conference: Pacific Northwest AES Section Meeting (Nov 2017)
Authors:
Joseph Anderson at University of Washington Seattle
Joseph Anderson
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Abstract

Originally developed and commercialized as a practical ”full 3D” sound recording and reproduction technique in the 1970s, with recent advancements in VR applications Ambisonics is enjoying a renewed interest. Offering both theoretical and functional tool-chains, Ambisonics is ideally suited as an adaptable and ”future proof” solution for 3D audio. In this discussion we’ll introduce the principal concepts of the Ambisonic technique and review how these are addressed by the tools found in the Ambisonic Toolkit (ATK) software package. Additionally, we’ll also offer demonstrations of practical projects created at the Center for Digital Arts and Experimental Media (DXARTS) leveraging the soundfield synthesis and signal processing techniques the ATK offers.
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Pacific Northwest Section of the AES
Wednesday, November 15, 2017
University of Washington, Raitt Hall 121
Seattle, WA, USA
Research Scientist
Center for Digital Arts & Experimental Media
University of Washington
Ambisonics & the ATK @ DXARTS
Joseph Anderson
Affiliate Assistant Professor, Composition
School of Music
University of Washington
Joseph Anderson — November 15, 2017 ATK @ DXARTS — PNW Section of the AES 2/38
Assigned Reading
D. Arteaga, “Introduction to Ambisonics,” Universitat Pompeu Fabra, Barcelona, Spain,
Lecture notes, Jun. 2017.
J. Daniel, “Représentation de champs acoustiques, application à la transmission et à la
reproduction de scènes sonores complexes dans un contexte multimédia,” PhD Thesis,
Université Paris 6, Paris, 2001.
M. Kronlachner, “Spatial Transformations for the Alteration of Ambisonic Recordings,”
Master’s Thesis, Graz University of Technology, Graz, Austria, 2014.
A. Politis, “Microphone array processing for parametric spatial audio techniques,” PhD
Thesis, Aalto University, Helsinki, Finland, 2016.
E. G. Williams, Fourier Acoustics: Sound Radiation and Nearfield Acoustical Holography.
London: Academic Press, 1999.
Joseph Anderson — November 15, 2017 ATK @ DXARTS — PNW Section of the AES 3/38
Ambisonics is...
Holographic
Periphonic
“Scene based”
Hierarchical
Rational
Convenient
Isotropic
Joseph Anderson — November 15, 2017 ATK @ DXARTS — PNW Section of the AES 4/38
Ambisonic Vocabulary
order encoding
decoding
B-format
A-format
HOA
NFC
Joseph Anderson — November 15, 2017 ATK @ DXARTS — PNW Section of the AES 5/38
Ambisonic Flavors
“Classic” B-format, aka Gerzonic
FOA
Furse-Malham, aka FuMa
HOA (≤3rd)
AmbiX
HOA
ACN-N3D (with NFC)
HOA
Joseph Anderson — November 15, 2017 ATK @ DXARTS — PNW Section of the AES 6/38
Some other software solutions...
Production
Blue Ripple Sound — Pro Audio
ambiX — Ambisonic plug-in suite
Research
Higher Order Ambisonics Library
Ambisonic Decoder Toolbox
Sound Field Synthesis Toolbox
SOFiA
Joseph Anderson — November 15, 2017 ATK @ DXARTS — PNW Section of the AES 7/38
ATK People
Joseph Anderson*Juan Pampin*Joshua Parmenter*
Michael McCrea*Trond Lossius†‡ Daniel Peterson*
Bergen Center for
Electronic
Arts
Center for Digital Arts and Experimental Media
*
†
‡
Joseph Anderson — November 15, 2017 ATK @ DXARTS — PNW Section of the AES 8/38
ATK @ DXARTS
DXARTS Sound Lab – Mid-field Spherical Array DXARTS Sound Lab – Near-field Hemi-spherical Array
DXARTS Media Lab – Mid-field Hemi-spherical Array DXARTS Sound Lab – Loudspeaker Measurement & Correction
Joseph Anderson — November 15, 2017 ATK @ DXARTS — PNW Section of the AES 9/38
ATK Platforms
Joseph Anderson — November 15, 2017 ATK @ DXARTS — PNW Section of the AES 10/38
ATK Objectives
Joseph Anderson — November 15, 2017 ATK @ DXARTS — PNW Section of the AES 11/38
ATK: ‘Think Ambisonic!’
Joseph Anderson — November 15, 2017 ATK @ DXARTS — PNW Section of the AES 12/38
ATK Paradigm
Joseph Anderson — November 15, 2017 ATK @ DXARTS — PNW Section of the AES 13/38
Encoding: Soundfield Authoring
OUTRS tetrahedral microphone array, courtesy Stephen Thornton
(www.michaelgerzonphotos.org.uk)
Soundfield microphone, Soundfield Ltd.
(soundfield.com)
UHJ
Joseph Anderson — November 15, 2017 ATK @ DXARTS — PNW Section of the AES 14/38
Encoding: Soundfield Authoring
Encoding Mono using
ATK for Reaper
Joseph Anderson — November 15, 2017 ATK @ DXARTS — PNW Section of the AES 15/38
A-format & B-format: ‘Think Ambisonic’
A-format
Synthesise complex
soundfields
Process soundfields
Joseph Anderson — November 15, 2017 ATK @ DXARTS — PNW Section of the AES 16/38
Soundfield Authoring: ‘Think Ambisonic’
Synthesis
In A-format
Diffuse / active soundfield
Followed by imaging
Joseph Anderson — November 15, 2017 ATK @ DXARTS — PNW Section of the AES 17/38
Soundfield DAFX: ‘Think Ambisonic’
Audio Effects
Process in A-format
Preserve imaging
Effect complete soundfield
→ Ambisonic DAFX!
?
?
?
?
Joseph Anderson — November 15, 2017 ATK @ DXARTS — PNW Section of the AES 18/38
ATK Imaging: Zoom
Zoom Transform
Dominance
Reshape Soundfield
Joseph Anderson — November 15, 2017 ATK @ DXARTS — PNW Section of the AES 19/38
ATK Imaging: Focus
Focus Transform
Dominance
Related
Reshape Soundfield
Joseph Anderson — November 15, 2017 ATK @ DXARTS — PNW Section of the AES 20/38
ATK Imaging: Push
Push Transform
Two metaphors:
Spatial Shelving-Filter
Re-align Tetrahedron
Reshape Soundfield
Joseph Anderson — November 15, 2017 ATK @ DXARTS — PNW Section of the AES 21/38
Decoding: Soundfield Monitoring
UHJ
Sky System One 5.1, Blue Sky International Ltd.
(abluesky.com)
Sky System One 2.1, Blue Sky International Ltd.
(abluesky.com) DT 990 PRO, beyerdynamic GmbH & Co. KG.
(www.beyerdynamic.com)
Joseph Anderson — November 15, 2017 ATK @ DXARTS — PNW Section of the AES 22/38
ATK Produced Works...
Joseph Anderson — November 15, 2017 ATK @ DXARTS — PNW Section of the AES 23/38
ATK Produced Works...
Joseph Anderson — November 15, 2017 ATK @ DXARTS — PNW Section of the AES 24/38
ATK Produced Works...
On Space recording plot Palais des Fêtes
Joseph Anderson — November 15, 2017 ATK @ DXARTS — PNW Section of the AES 25/38
ATK Produced Works...
Joseph Anderson — November 15, 2017 ATK @ DXARTS — PNW Section of the AES 26/38
ATK in Action...
End of
month!
Joseph Anderson — November 15, 2017 ATK @ DXARTS — PNW Section of the AES 27/38
ATK in Practice
Ambisonic Toolkit
(SuperCollider Library)
Quick Look
Joseph Anderson — November 15, 2017 ATK @ DXARTS — PNW Section of the AES 28/38
ATK in Practice
Ambisonic RIR from the Fort Worden Cistern
Ewa Trebacz & Josiah Boothby
Seattle P-I
Joseph Anderson — November 15, 2017 ATK @ DXARTS — PNW Section of the AES 29/38
ATK in Practice
VR & Holographic Sound Synthesis with the ATK
Daniel Peterson & Martin Jarmick
Joseph Anderson — November 15, 2017 ATK @ DXARTS — PNW Section of the AES 30/38
ATK in Practice
AmbiVerbSC: An Ambisonic tank reverb model for SC3
James Wenlock
Joseph Anderson — November 15, 2017 ATK @ DXARTS — PNW Section of the AES 31/38
ATK, Future Development...
Coming Soon (SC3)...
Soundfield Analysis
Soundfield (matrix)
transform display
On the Horizon...
T-design A-format
ADT integration
Revised beam-forming
model
HOA-NFC! (SC3 &
Csound)
Joseph Anderson — November 15, 2017 ATK @ DXARTS — PNW Section of the AES 32/38
ATK, WTF?
?
?
?
?
Questions...?
Joseph Anderson — November 15, 2017 ATK @ DXARTS — PNW Section of the AES 33/38
References
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Joseph Anderson — November 15, 2017 ATK @ DXARTS — PNW Section of the AES 34/38
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Joseph Anderson — November 15, 2017 ATK @ DXARTS — PNW Section of the AES 35/38
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Joseph Anderson — November 15, 2017 ATK @ DXARTS — PNW Section of the AES 38/38
dxarts.washington.edu
www.ambisonictoolkit.net
Guides/Intro-to-the-ATK
github.com/ambisonictoolkit
joanders@uw.edu
Thanks!!
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ADAPTING ARTIFICIAL REVERBERATION ARCHITECTURES FOR B-FORMAT SIGNAL PROCESSING
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  • Jun 2009
Auralisation ray-traced volume modeling reverberation methods presently appear to be a preferred approach for generating surround sound reverberation. However, a wide literature describing various architectures for artificial reverberation filters is extant. Many of these alternative delay-line methods give distinct performance advantages, in that they are not reliant upon convolution or volume modeling, and allow a variety of tonal and spatial parameters to be modified independently. The authors describe a method to expand or adapt these known architectures to an Ambisonic B-format context, and provide an illustrative example native B-format reverberator. Central to this approach is the adaptation of scattering junctions to a B-format context and the use of B-format spatial image transformation techniques.
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This demonstration provides a hands on introduction to the powerful soundfield authoring, transformation and playback techniques made available to the SuperCollider3 user through the Ambisonic Toolkit (ATK). The ATK brings together a number of classic and novel tools for the artist working with Ambisonic surround sound and makes these available to the SuperCollider3 user. The toolset is intended to be both ergonomic and comprehensive, and is framed so that the user is enabled to ‘think Ambisonic’. By this, the ATK addresses the holistic problem of creatively controlling a complete soundfield, facilitating spatial composition beyond simple placement of sounds in a sound-scene. The artist is empowered to address the impression and imaging of a soundfield—taking advantage of the native soundfield-kernel paradigm the Ambisonic technique presents. Along with powerful soundfield transforms (spatial filtering), the ATK provides a comprehensive set of Ambisonic encoders (including pseudo-inverse encoders) and decoders (5.1, binaural, UHJ, full-3D) allowing the artist to thoroughly leverage the potential of the Ambisonic technique. Keywords: ambisonics, surround sound, spatialisation, spatial filtering, digital audio effects Links: ambisonictoolkit.net
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The Simulation of Moving Sound Sources
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  • Jun 1977
A digital computer was used to generate four channels of information, which are recorded on a tape recorder. The computer program provides control over the apparent location and movement of a synthesized sound in an illusory acoustical space. The method controls the distribution and amplitude of direct and reverberant signals between the loudspeakers to provide the angular and distance information and introduces a Doppler shift to enhance velocity information.
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Microphone array processing for parametric spatial audio techniques
Thesis
  • Nov 2016
Reproduction of spatial properties of recorded sound scenes is increasingly recognised as a crucial element of all emerging immersive applications, with domestic or cinema-oriented audiovisual reproduction for entertainment, telepresence and immersive teleconferencing, and augmented and virtual reality being key examples. Such applications benefit from a general spatial audio processing framework, being able to exploit spatial information from a variety of recording formats in order to reproduce the original sound scene in a perceptually transparent way. Directional Audio Coding (DirAC) is a recent parametric spatial sound reproduction method that fulfils many of the requirements of such a framework. It is based on a universal 3D audio format known as B-format and achieves flexible and effective perceptual reproduction for loudspeakers or headphones. Part of this work focuses on the model of DirAC and aims to extend it. Firstly, it is shown that by taking into account information of the four-channel recording array that generates the B-format signals, it is possible to improve both analysis of the sound scene and reproduction. Secondly, these findings are generalised for various recording configurations. A further generalisation of DirAC is attempted in a spatial transform domain, the spherical harmonic domain (SHD), with higher-order B-format signals. Formulating the DirAC model in the SHD combines the perceptual effectiveness of DirAC with the increased resolution of higher-order B-format and overcomes most limitations of traditional DirAC. Some novel applications of parametric processing of spatial sound are demonstrated for sound and music engineering. The first shows the potential of modifying the spatial information in the recording for creative manipulation of sound scenes, while the second shows improvement of music reproduction captured with established surround recording techniques.The effectiveness of parametric techniques in conveying distance and externalisation cues over headphones, led to research in controlling the perceived distance using loudspeakers in a room. This is achieved by manipulating the direct-to-reverberant energy ratio using a compact loudspeaker array with a variable directivity pattern. Lastly, apart from reproduction of recorded sound scenes, auralisation of the spatial properties of acoustical spaces are of interest. We demonstrate that this problem is well-suited to parametric spatial analysis. The nature of room impulse responses captured with a large microphone array allows very high-resolution approaches, and such approaches for detection and localisation of multiple reflections in a single short observation window are applied and compared.
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