Presented at the 21st International Conference on Auditory Display (ICAD2015), July 6-10, 2015, Graz, Styria, Austria.With the emergence of electroacoustic music, spatial figures have
become part of the musical vocabulary of many composers. But
the perception of auditory trajectories has received scant attention
in the scientific literature. This study aims at determining under
which conditions simple common spatial figures (such as circles,
squares and triangle) can be perceived by a listener positioned in
the center of a loudspeaker arrays. In a series of listening tests, we
investigate the effect of rendering techniques (VPAB vs. WFS),
reverberation (dry vs. modeled reflections) and sound velocity on
spatial figure identification performance

Boissinot, Julien

Camier, Cédric

Féron, François-Xavier

Guastavino, Catherine

International audienceWith the emergence of electroacoustic music, spatial figures have become part of the musical vocabulary of many composers. But the perception of auditory trajectories has received scant attention in the scientific literature. This study aims at determining under which conditions simple common spatial figures (such as circles, squares and triangle) can be perceived by a listener positioned in the center of a loudspeaker arrays. In a series of listening tests, we investigate the effect of rendering techniques (VPAB vs. WFS), reverberation (dry vs. modeled reflections) and sound velocity on spatial figure identification performance

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Tracking Moving Sounds : Perception of Spatial Figures

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The 21st International Conference on Auditory Display (ICAD–2015) July 8-10, 2015, Graz, AustriaTRACKING MOVING SOUNDS: PERCEPTION OF SPATIAL FIGURESCédric Camier ?(a,b), François-Xavier Féron(c), Julien Boissinot (b), Catherine Guastavino (a,b)(a)Multimodal Interaction LabSchool of Information Studies,McGill University3661 Peel St. Montreal, Canada H3A1X1.(b) Center for Interdisciplinary Research in Music Media and TechnologySchool of Information Studies,McGill University527 Sherbrooke St. West Montreal, Canada H3A 1E3.(b) CNRS, Laboratoire Bordelais de recherche en InformatiqueLaBRI, UMR 5800, F-3340033400 Talence, France ?cedric.camier@mail.mcgill.caABSTRACTWith the emergence of electroacoustic music, spatial figures havebecome part of the musical vocabulary of many composers. Butthe perception of auditory trajectories has received scant attentionin the scientific literature. This study aims at determining underwhich conditions simple common spatial figures (such as circles,squares and triangle) can be perceived by a listener positioned inthe center of a loudspeaker arrays. In a series of listening tests, weinvestigate the effect of rendering techniques (VPAB vs. WFS),reverberation (dry vs. modeled reflections) and sound velocity onspatial figure identification performance.1. INTRODUCTIONWhile spatial considerations in music date back to the Renais-sance, space only earned its place among critical musical attributesin the second half of the 20th century with the development ofspatial sound reproduction and the emergence of electroacousticmusic. However, the extent to which trajectories conceived in themind of the composer, implemented by sound engineers, musicalassistants and performers can be perceived by listeners remains anopen question. The present study focuses on closed spatial soundfigures inside of a circular array of loudspeakers based on a reviewof musical works using dynamic sounds localization and spatialrendering techniques. We investigate the conditions under whichthese figures can be perceived as a function of the rendering tech-nique, reverberation of the room and the velocity of the movingsound. Previous trajectory studies have used other report methods,such as asking subjects to draw the trajectory [1]. Investigation ofperceived trajectories in spatial audio is still in need of formali-sation, so the three-alternative forced choice method intended foruse here should add to that conversation.This work is licensed under Creative Commons Attribution NonCommercial 4.0 International License. The full terms of the License areavailable at http://creativecommons.org/licenses/by-nc/4.02. SPATIAL TRAJECTORIES IN CONTEMPORARYMUSICWith the emergence of electroacoustic music in the 1950s, com-posers became interested in positioning and moving sounds inspace. Since the development of loudspeaker orchestras in the be-ginning of the 1970s (gmebaphone [2] and acousmoniums [3]), theinterpretation of electroacoustic composition consists in a spatialinterpretation which tends to explore spatial effects mostly basedon manual amplitude panning [4]. According to Van de Gorne [4],the ideal room acoustics to perform spatial interpretation is a dryroom or a open field, as reverberation is hypothesized to havea detrimental effect on spatial interpretation precision. In 2008,Peters [5] conducted a web-based survey with 52 composers andsonic artists to better understand how they use spatialization, whatspatial aspects are essential and what functionalities spatial audiosystems should strive to include or improve. Immersion was re-ported as one of the most desirable effect produced by a spatialreproduction system which was linked to source width and spatialreverberation simulation. Furthermore, respondents highlightedthe need to consider room acoustics in spatial rendering softwaretools.3. DYNAMIC SOUNDFIELD SYNTHESISStatic soundfield synthesis has been extensively studied over thelast decades and allows accurate and robust simulation results [6].However, dynamic soundfield synthesis implies the reproductionof physical alterations of the sound waves produced by movingsources. The sound waves experience compression or expansionrelated to the direction of motion, which leads to a Doppler effectconsisting in a pitch shift and an amplitude modification. Typicalimplementation of soundfield synthesis do not take the Dopplereffect into account. Rather, dynamic virtual soundfields are dis-cretized as a sequence of stationary snapshots. Depending onthe duration of each snapshot, this discretization may lead to aDoppler-like frequency shift. Depending on the technique used,this results from a compression/depression of successive loud-2015) July 8–ICAD 2015 - 308The 21st International Conference on Auditory Display (ICAD–2015) July 8-10, 2015, Graz, AustriaFigure 1: Experimental setup in the CIRMMT Spatial Audio Lab.Both loudspeaker arrays consist of equally spaced loudspeakers ona 3.5-m circle in the horizontal plane (16 Genelec for the top one,48 B & W for the bottom one).speaker contribution radiation (e.g. VBAP) or from time warping(e.g. WFS) rather than from the actual Doppler effect between thevirtual source and the listener. As shown by Franck [7] and Ahrensand Spors [8, 9] for WFS, these artefacts occur in conventional im-plementations of WFS, but can be avoided by taking into accountthe physics of soundfield generated by moving sources.4. APPARATUSThe experimental setup is shown in Fig. 1 with two circular loud-speaker arrays with a diameter of 3.5 m in the hemi-anechoic Spa-tial Audio Lab of the Centre for Interdisciplinary Research in Mu-sic Media and Technology (CIRMMT) in Montreal (Canada). Thedry room is 5.40 m (W) ⇥ 6.40 m (L) ⇥ 3.60 m (H) with a mea-sured Reverberation Time (RT60) and Early Decay Time of 0.09s and 0.28 s respectively. The first circular array consisted of 16Genelec 8040A (Genelec, Iisalmi, Finland, frequency range 48 -20,000 Hz) regularly spaced in the horizontal plane. The secondloudspeaker array is located 10 cm below and consists of regularlyspaced 48 M1 Bowers & Wilkins loudspeakers.Stimuli are generated using a Max/MSP object using VectorBase Amplitude Panning (VBAP) [10] implemented in a previousstudy [11] in order to guarantee smooth angle variations at veryhigh velocities. The MAX/MSP object was programmed in JAVAlanguage (with the MXJ functionality) to sample the angle param-eter at the audio sample rate and allow modeled primary and sec-ondary reflections upon four virtual walls while omitting specularreflections.5. PROCEDUREOn each trial, participants are presented with a spatial figurearound them and asked to indicate which of three figures they per-ceived (triangle, square and circle) using a three-alternative forcedchoice. We manipulate 3 independent variables in a series of ex-periments, namely reverberation (dry, vs. modeled 1st and 2d re-flections), the spatial rendering techniques (VPAB vs. WFS), aswell as the velocity of the moving sound. We hypothesize thatreverberation will have a detrimental effects on the perception ofspatial figures as suggested by Van de Gorne [4]. In addition, theartifacts introduced by the spatial rendering systems could inter-fere with dynamic localization, especially at high velocities.Binomial tests will reveal which figures can be correctly iden-tified in each experimental condition. The findings will determineconditions under which closed spatial figures can be perceived bya listener in the center of a circular array. Incorrect answers willinform us on misidentifications and confusions between figures.Depending on the results of these experiments with the 3 ba-sic figures, we will extend our investigation to a wider range offigures at various distances from the listener. Another extensionwill involve manipulating the spectral content of the sounds basedon the observation that low frequency sounds moving in a circlearound the listener can be tracked at higher velocities than higherfrequency sounds [12]. Furthermore, we will conduct acousticalmeasurements with a binaural mannequin to complement the anal-ysis of the perceptual tests and determine which psychoacousticalcues are critical to track sound trajectories.6. ACKNOWLEDGMENTSThis research was supported NSERC (RGPIN 327392-13) grantand a William Dawson award (McGill University). The authorswould like to thank Olli Rummukainen for his assistance with theexperimental setup.7. REFERENCES[1] M. Gorzel, G. Kearney, C. Masterson, H. Rice, andF. Boland, “On the perception of dynamic sound sources inambisonic binaural renderings,” in Audio Engineering Soci-ety 41st International Conference: Audio for games., Lon-don, 2011.[2] C. Clozier, “Un instrument de diffusion : le gmebaphone,”Musique et recherche, vol. L’espace du son, pp. 56–57, 1988.[3] F. Bayle, Musique Acousmatique, propositions positions,Buchet/Chastel, Ed. INA, 1993.[4] A. Van de Gorne, “L’interprétation spatial. essai de formali-sation méthodologique.” Demeter, 2002.[5] N. Peter, “Sweet [re]production. developing sound spatial-ization tools for musical applications with emphasis on sweetspot and off-center perception,” Ph.D. dissertation, Depart-ment of Music Research Schulich School of Music McGillUniversity, 2010.[6] R. Rabenstein and S. Spors, Multichannel Sound FieldReproduction, springer ed., J. Benesty, M. Sondhi, andY. Huang, Eds. Berlin: Springer Handbook on Speech Pro-cessing and Speech Communication, 2007.[7] A. Franck, A. Gräfe, T. Korn, and M. Strauss, “Reproduc-tion of moving sound sources by wave field synthesis - ananalysis of artifacts,” in The proceedings of the AES 32nd in-ternational conference, Hillerod, Denmark, Sept. 2007, pp.188–196.[8] J. Ahrens and S. Spors, “Reproduction of moving virtualsound sources by wave field synthesis: An analysis of ar-tifacts,” in 32nd Int. Conference of the AES, 2007.[9] ——, “Reproduction of moving virtual sound sources witha special attention to the doppler effect,” in 124th Conv. ofAES, 2008.2015) July 8–ICAD 2015 - 309The 21st International Conference on Auditory Display (ICAD–2015) July 8-10, 2015, Graz, Austria[10] V. Pulkki, “Virtual sound source positionning using vec-tor base amplitude panning,” Audio Engineering Society,vol. 45, no. 6, pp. 456–466, 1997.[11] C. Camier, J. Boissinot, and C. Guastavino, “Does reverber-ation affect upper limits for auditory motion perception,” inICAD, vol. Submitted, Graz, Austria, 2015.[12] F.-X. Féron, I. Frissen, J. Boissinot, and C. Guastavino, “Up-per limits of auditory rotational motion perception,” Journalof Acoustical Society of America, vol. 128, no. 6, pp. 3703–3714, 2010.2015) July 8–ICAD 2015 - 310

Tracking moving sounds: Perception of spatial figures

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Tracking moving sounds: Perception of spatial figures

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Hal-Diderot

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