2010 auditory tactics: a sound installation in public space using beamforming technology

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In recent decades, the development of affordablemultichannel sound cards and computer-based digital audiohas generated an unprecedented availability of multichan-nel sound. Although artistic interest in natural and artificialspatial sound is not new [1], these recent developments havetransformed artists relationships with sound spatialization.

Originally restricted by expense to work by world-renownedcomposers (Varse, Stockhausen, Xenakis [2]), spatial soundis now common in sonic art and electroacoustic music as wellas in popular media.

In 2006, we were invited to produce a spatial sound instal-lation in a public space in Montral [3] for the Pure-DataConvention 2007 [4]. At the conceptual level, we were inter-ested in the interplay between various auditory spheres andthe concomitant auditory tactics. The term auditory tacticsrefers to the contextual listening attitudes and competenciesadopted or developed to achieve specific auditory tasks whendifferent acoustical environments or aural architectures areencountered. As we have witnessed an explosion of mobiletechnologiesWalkmans, MP3 players, mobile phones and

noise-cancellation earphonesthat by artificial means al-low for sonic and spatial cohabitation of personal and publicspheres, we decided to address this theme in our installation.Our idea was to attempt to interfere and play with the audi-tory tactics of passersby in public space by projecting soundsassociated with more private and intimate spheres.

Auditory Tactics was a novel exploration in beamformingfor sound reproduction. This technology allows the creationof directional sonic beams with interesting reflective proper-ties. The possibility to create sonic illumination and shadowzones by remote means inspired us with respect to the afore-mentioned idea. Using a custom-built system, this, to our

knowledge, is the first time thistechnology has been applied to asound installation in a public space.

This paper aims to present theresults and lessons learned fromthis experience while balancing the

social, artistic and technical dimen-sions of the project. We report anddiscuss both the conceptual andpractical elements of the projectthroughout.

The first section of this paper introduces the artistic andtechnical background to this project along with our initialmotivations. The second section describes the creation pro-cess, and the conclusion discusses the results and observationsdrawn from the installation.

BACKGROUNDANDMOTIVATIONS

Spatial SoundAny perceived sound is naturally spatial. Indeed, sound propa-gation in air is space-dependent, as is human sonic perception.Given this naturally three-dimensional auditory experience, to

what does the expression spatial sound refer in sonic art andacoustic engineering? It originates from a diachronic perspec-tive on sound technologies, which in their infancy constrictedthe reproduced spatial auditory experience to a monophonictransmission line. It may be that this major technologicaldistortion of sonic space suddenly revealed the aesthetic po-tential of spatial sound, suggesting novel possibilities beyondincreased realism.

Since the beginning of the modern technological era, spa-tial sound has been explored and continuously redefined byartists in electroacoustic concerts, sound installations and per-formances with or without the help of technological develop-ers or industry engineers. There are as many motivations forand conceptions of spatial sound as there are artists. It is pos-sible, however, to note a dominant feature: Spatial sound typi-cally involves the relative movements of the perceived soundand the audience. For Auditory Tactics, we address these twomovements.

In addition, we endorse spatial-sound art as an avenue tomove beyond spatial sound as a perceptually and aestheticallypleasurable presentation mode and seek to provoke contem-plation and critical reflection on listening, hearing, auditoryhabits,sound culture and their history by conscious manipu-

2010 ISAST LEONARDO, Vol. 43, No. 5, pp. 426433, 2010 427

A R T I S T S A R T I C L E

Auditory Tactics:A SoundInstallation in Public SpaceUsing Beamforming Technology

Philippe-Aubert Gauthierand Philippe Pasquier

A B S T R A C T

The term auditory tacticsrefers to the contextual listen-

ing attitudes and competencies

adapted to various private

and public auditory contexts,

spheres and aural architectures.

Auditory Tactics,created for

the Pure-Data Convention 2007

in Montral, is a spatial soundinstallation designed to inter-

fere and play with the auditory

tactics of passersby in a public

space by projecting sounds

from more private spheres. The

novelty of the authors work

is the use of beamforming: a

sound projection technology that

allows the creation of directional

sonic beams resulting in sonic

illumination and shadow zones

that dynamically interact with

architectural surfaces. The

authors report the results and

lessons of this first artistic

experiment with sound beams

as a creative sound-projectionmethod.

Philippe-Aubert Gauthier (sound artist), Groupe dAcoustique de lUniversit

de Sherbrooke, Universit de Sherbrooke, 2500 boul. de lUniversit, Sherbrooke,Qubec, J1K 2R1 Canada; Centre for Interdisciplinary Research in Music, Mediaand Technology, McGill University. E-mail: .Web: .Philippe Pasquier (sound artist), School of Interactive Art and Technology, Simon FraserUniversity, 250-13450 102 Avenue Surrey, BC, V3T 0A3 Canada. E-mail: .Web: .See for supplemental files related tothis article.

Article Frontispiece. Installation at Concordia University.The picture shows the architectural complexity.( Philippe-Aubert Gauthier)

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428 Gauthier and Pasquier, Auditory Tactics

ditory sphere involves different types ofacoustic arenas or sound sources. Whileone is navigating socially through thesespheres, expectations about acoustic are-nas trigger or emphasize various auditorytactics, communicative behavior, andsound quality or aesthetics. As stated byBlesser and Salter: Social expectationsdetermine the properties, especially size,of an acoustic arena and social behaviorthen adapts to available arenas. . . . Aural

architecture [which plays a part in thecreation of acoustic arenas] is not onlythe physical design of a space, but alsopart of a complete social system [12].

We believe that, just as does aural archi-tecture, spatial sound technologies forpublic spaces also take part in a completesocial system. Since acoustic arenas influ-ence social cohesion, technological mod-ifications of acoustic arenas are, perhaps,the most salient feature of sound devicesthat aim at the cohabitation of privateand public auditory spheres.

In accordance with these conceptions,our intention was to interfere and play

with the auditory tactics used in a publicspace by infusing the space with spatialsound usually associated with privatespaces. We wanted to exploit these inter-ferences as an aesthetic effect, an explor-atory avenue, a conceptual tool and anartistic statement to encourage auditoryspatial awareness and critical reflectionconcerning the technologies that con-tribute to the social shaping of listeningand hearingtechnological devices that,by their banality [12], surreptitiously in-trude and modify our habits.

Beamforming technology can manip-ulate the regions of space where soundis audible by shaping and controllingthe spatial and directional radiation ofsound. It can create and manipulateacoustic arenas intended for the spatialcohabitation of the intimate, personaland public spheres. The creation andrestructuring of these acoustic arenasand communities has already been ini-tiated by technologies such as portableheadsets and mobile telephones. Unlikethese two examples, in Auditory Tactics,BF is used to create a private sonic spaceremotely.

However, these ideas, as developed bySterne [13], should be treated with greatcare. Such a fragmentation of the acous-tic arena into private arenas is not solelyor deterministically related to technolog-ical devices and innovations. Indeed, var-ious private-space listening techniques,

with few technological supports, alreadyexisted prior to the personal sound de-

vices mentioned in the introduction.One should also keep in mind that prior

archetypal private or semi-privatespace.

2. The city (or public shell): an anony-mous shell where spontaneous ac-tions, movements and expressionsare subtly controlled, for example,personal scheduling according totransport timetables, paying fortransport and managing agen-das with respect to institutionsopening hours. The archetypal

public space.Different auditory tactics, listening strate-gies and auditory expectations character-ize these shells. We do not listen in thesame way when we are in our bathroomsas when in an airport terminal [9]. Differ-ent auditory tactics come into play whenlistening to a friend in a crowded caf, ona mobile phone or in a quiet living room.Listening strategies are also affected bytheir cognitive context, for example,

job- or performance-related listening(required of pilots, telegraph operatorsat the end of the 19th century, etc.), orleisure-oriented listening. Technologicaldevices also play a part in the creation, or

variation, of new auditory tactics on thebasis of previous auditory experiences,tactics and sonic cultures [10].

These definitions of environmen-tal shells coincide with the conceptionof auditory spheres as introduced byBlesser and Salter in their presentationof acoustic horizons and arenas [11].

An acoustic arena is defined as a regionwhere listeners share the ability to heara given sound source. Typically, each au-

lation of the medium and its social sig-nification. Using a new sound device asan artistic medium, we hope to encour-age curiosity and reflection about theseconcepts.

Spatial sound reproduction tech-niques can be classified as either (1)

perception simulation (binaural sound,L-channel stereophony [5], etc.) or (2)sound-field simulation(wave field synthe-sis, classic Ambisonics, etc.) [6]. Beam-

forming (BF) technology belongs in thesecond category. However, while it is a ge-neric technique commonly used in suchareas as medical ultrasound scanning,ground exploration and sonar, researchon the use of BF for innovative soundreproduction has just begun [7]. Theonly commercial BF device available atthe time of writing is for a conventionalpurpose: virtual 5.1 surround sound (asexemplified by Yamahas Digital SoundProjector). Much remains to be exploredin using BF for spatial sound within anartistic context.

Artistic Intention: Private andPublic Spaces, Spatial SoundTechnologies, Acoustic Arenas

According to Moless psychology ofspace [8], our spatial relations with ourenvironment are organized in concentricshells. The most extreme shells are

1.The home (or intimate/personal/conversational shell): a personal-ized space open to free expres-sion of private activities, actions,movements and thoughts. The

Fig. 1. (a) Linear 16-loudspeaker array. Loudspeakers are marked by filled circles. Positionis described by rectangular (x,y) or polar (r,) coordinates. Wave fronts created by individ-ual loudspeakers are marked by dashed lines. (b) Scheme of sound beam with eight loud-speakers (white circles). The order of emission is indicated. ( Philippe-Aubert Gauthier)

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Gauthier and Pasquier, Auditory Tactics 429

Auditory Tacticsinvolved a total of 941original samples grouped in 31 thematic

banks. These banks spanned a variety ofsounds: men and women breathing, whis-pering, laughing, screaming and speak-ing in shrill voices, various vocal soundsor effects, vocoder voices, drones andshort text excerpts from various authors.The excerpts were related to the placeof the individual or institutional voice inpublic space and the coercive control of

voices and acoustic communities. A finebalance between concrete realism andmusical acousmatic treatments was at-tempted.

Generative CompositionThe exhibition took place in the publichall of the Engineering and Arts Faculty(EV) Building of Concordia University(Montral, Canada) from 22 August to22 September 2007, with continuous ac-cess. We were consequently concerned

with the creation of a generative sound

stronger in the beam direction (see Fig.2b), there is some softer residual sound

radiation in all directions.The signal processing for beamform-ing is illustrated in Fig. 3 [15]. Thecascaded delay modules have the sametime delay. Varying this time delay willrotate the beam. The time delay corre-sponds to the time needed for a plane

wave with propagation angle beam topropagate from a given loudspeaker to itsneighbor. We used a time delay of D = dcos(beam)/c where d is the loudspeakerseparation distance and c the speed ofsound (~344 m/s).

This signal processing algorithm wasachieved in real time using the Pure-Data programming environment. Weexperimented with eight audio channelsassigned to eight beams. The array canbe seen in the Article Frontispiece andFigs 4 and 5.

CREATIONPROCESS

Sound MaterialAt the heart of what we wanted to ex-press with Auditory Tacticslie the selectionand transformation of sound materialin relation to our interest, that is, theintertwined influences of augmentedlistening and sound projection tech-nologies in reshaping their users dailyauditory tactics. The human voice, as aprimary sound material, was an obviouschoice to evoke the private or personalsphere while still maintaining a relation

with the public space. Indeed, althoughcriticized by Sterne[16], speech is gen-erally perceived, in a broad sense, as themanifestation of a kind of pure interi-ority, the primary site of the individual.

cultural contexts influence the selectionand shaping of emerging technologies,

which are often the more or less con-scious product of collective wishes andfuturistic visions. On that matter, the an-alytical program proposed by Sterne inThe Audible Pastposits the possible basesand articulations of a technology-relatedart practice that operates in sound arts.Under that influence, we hope that ourapproach presents an equilibrium be-

tween historical, cultural, artistic andtechnological vantage points. Indeed,our artistic practice involving technologi-cal devices and innovations is based ona conscious mix and superimposition ofmany aspects, references, sounds, etc., sothat audiences might draw from an accu-mulation of elements and

critical inter-pretations. As the sharing and discussionof multidisciplinary knowledge aboutthe technological devices investigatedis part of our artistic intention regard-ing the critical understanding of soundtechnologies, this paper also contributesto our artistic agenda. The next sectionintroduces the technical aspects of BFtechnology.

Sound BeamsAn acoustical beam is a sound that propa-gates with a hyper-directive radiation. BFrelies on loudspeaker arrays (Fig. 1) tocreate such beams.

In order to understand this technol-ogy, let us first assume that a loudspeakeremits a spherical wave [14]. Examples ofspherical waves emitted by loudspeak-ers are shown as dashed lines in Fig. 1afor L = -7 and L = 0 (where L is the loud-speaker index). We next recall that the to-tal sound field created by a set of sourcesis simply the sum of the individual soundfields created by all of the sources.

The basic idea of BF is to use a loud-speaker array with a delayed emission forthe individual loudspeaker to create di-rective radiation. Figure 1b illustrates theprocess. Each dashed line represents a

wave front created by a loudspeaker. Theemission order is indicated: L = -2 emitsfirst and L = 5 emits last. In this figure,it can be seen that the wave fronts arealigned in space for the angular directionbeam(beam direction). This alignment(thick black lines) corresponds to a con-structive interference: All the individual

wave fronts add up to create a strongerwave front. For other directions, the wavefronts are not aligned and interfere withone another: The sound radiation hasa lower sound level. Figure 2 shows anemission of three consecutive impulsesby a single source (a) and by an array (b).Note that while the sound amplitude is

Fig. 2. (a) Snapshot in time of the theoretical sound field (three consecutive impulses)produced by a single loudspeaker. (b) Snapshot of the sound field produced (threeconsecutive impulses) by a beamformer (

beam= 105). Radiation is directive: There is

an intensification of sound in a given direction (marked by white dashed elliptical line),the illumination zone. ( Philippe-Aubert Gauthier)

Fig. 3. Schematic representation of acascaded-delay chain for beamforming.( Philippe-Aubert Gauthier)

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430 Gauthier and Pasquier, Auditory Tactics

lic presentation of Auditory Tacticssup-ported our conceptual interest. It was anarchetypal public space that allowed us toimplement our artistic intentions. How-ever, this type of public space also came

with factors that constrained the logisticsof the project, including security, admin-istration, planning and scheduling.

Spatial Sound EffectsWe were initially interested in investigat-

ing two particular spatial effects (Fig. 6).The first effect uses BF to remotely createprivate sonic arenas in a heterogeneoussonic space to challenge the default audi-tory tactics of people immersed in varioussound beams. Two beams scanned thespace (from -90 to +90) while two beams

were fixed to angles close to 0 and 180.People within these illumination zones(Fig. 6a) received a sonic content about16 times louder than people in shadowzones. This effect was used to materializethe idea of superimposing the private au-ditory sphere on the public one. People

in viewing distance of each other had pri-vate, personal access to different audiocontents and loudness balances.

The second effect exploited the re-flexivity of the beams. The array wasplaced in an alcove above eye level, andsix sound beams were projected against

ing students, faculty and staff as well as

the general public coming and goingfrom the building basement, whichhosts a subway station, a gym and smallstores. The Article Frontispiece andFig. 4 show the loudspeaker array atConcordia.

The selection of this site for the pub-

composition [17] that would stimulate

listening over the entire exhibition time.We had explored generative sound com-position in previous works [18]. Genera-tive composition operates at the macrolevel of the composition, allowing designof large-scale composition structures

without dealing with every detail.We created a macro-scale structure

based on a 24-hour cycle. Six time peri-ods were created; each relied on differ-ent sample banks and involved a differentimplementation of sampler control andadaptive mixing.

Night-time sounds were a combination

of soft breaths and intimate, soft sounds.Morning sounds were a continuation ofthe night sounds, with murmurs, laugh-ter and more active sounds. It was an in-timate, proximate and gentle awakening.

At noon, these soft and natural soundswere replaced by vocoder and syntheticvoices (whispers, sometimes with am-plified drones) reading a plethora oftext excerpts. Shrill voices and groansinvaded the afternoon, with a hint ofuncertainty, stress and revolt. Followingthis progression, the evening was char-acterized by more intense and impulsive

vocal sounds and marked screams, withsynthetically altered voices. The eveningreconnected to the nocturnal over a longprogressive transition from excitementto blackouta deep sleep.

Public SpaceThe EV Building is located on St-Cath-erine Street, one of the busiest axes ofdowntown Montral. The hall is occu-pied and traversed by arts and engineer-

Fig. 4. Installation at Concordia University. Faculty of Fine Arts (FOFA), Concordia Uni-versity. ( Philippe-Aubert Gauthier. FOFA Gallery Vitrines: Jessica Auer and AndreasRutkauskas, photography.)

Fig. 5. Fabrication. The final array in Vidographes PARC. ( Philippe-Aubert Gauthier)

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Gauthier and Pasquier, Auditory Tactics 431

whisper the projected sound, thus pro-viding a strong impression of intimatelistening. The sound localization wascompletely dissociated from the array.This phenomenon is illustrated in Fig. 7.The direct sound reached the listenersears first. The reflected beam arrived

just milliseconds later. The greater am-plitude of the beam reflection (illumi-nation zone) would then circumvent theprecedence effect [19]. Consequently, a

listener located in the encircled region inFig. 7 might localize the sound anywherebetween the direct wave front incidenceand the reflected BF wave front inci-dence. The synergy of this technical arti-fice and our artistic intention was clear,as soft whispering typically reinforcesthe idea of private acoustic arenas andspheres. This whispering effect should befurther explored in future beamformingexperiments.

Analysis of the Results. Several factorsinfluenced the perception of the piece.Firstly, we observed how the soundscape

of the hall influenced the auditory spa-tial awareness of the listeners. As the leveland complexity of the original sound-scape increased, the attention competi-tion between the ambient soundscapeand the sound installation rose as well.It is clear that the spatial smoothness ofthe transition between illumination andshadow zone was not drastic enough tosurprise the passersby. It would requiremore than a 12 dB difference to dilutethe sound shadows in the ambient noise

while making it strongly audible in theillumination zone. Secondly, the intricategenerative sound composition and theuse of eight simultaneous sound beamscreated a complex spatial sound entitythat uninformed audiences tended toexperience as a whole. While creatinga rich experience of spatial sound, thismay have obscured the transitions fromillumination to shadow zones.

Architectural factors were also influ-ential: The corridor shape of the hallcreated zones where the audience was

to be sufficient to efficiently explorethe spatial effects and themes describedearlier.

On-Site Perception of Sound Beams.As expected, passersby were surprised

by the sounds they perceived that didnot fit the public space they occupied.Intrigued, they typically searched for thesource of these sounds. It was found thatthe audience had to be informed aboutsound beams in order to perceive thebeam illumination and shadow zones assuch. Indeed, such information tends toencourage active listening. The interac-tion of the beams with the architecture

was more clearly and readily perceivedwhen listeners were informed about whatspatial sound features they should listenfor. Listeners typically perceived the spa-tialized sounds and their interaction withthe building, that is, positioning soundsin surprising places, or simply blurringtheir sound localization.

One of the most interesting effects ob-tained was the whispering wall. Whenthe listener stood near a wall and wassimultaneously exposed to both the di-rect sound from the array (due to beamimperfections) and the reflected beamfrom the wall, the wall appeared to softly

the facing wall. An example of a bounc-ing illumination zone is shown in Fig. 6b.Depending on which illumination zone(direct or reflected) the listener stoodin, the perceived sound source was local-

ized as either the array or the reflectivesurface. The expected result was that theaudience would perceive the sounds asif they were emanating from the walls(either from static or moving reflectionzones).

RESULTS, OBSERVATIONSANDFUTUREPERSPECTIVE

ResultsBeamforming. Preliminary listeningtests in the space of the art center Vido-graphe confirmed the existence of sonic

illumination and shadow zones. Thetransition from illumination to shadow

was progressive and continuous, as illus-trated in Fig. 2. Theoretically, the illumi-nation zone (i.e. in the beam) shouldinvolve a 12 dB gain in comparison withthe shadow zone (outside the beam),that is, it should be 16 times stronger(when using 16 loudspeakers).

The fact that the illumination andshadow zones differ by 12 dB might de-ceive the most informed segment of theaudience, who tend to imagine soundbeams more sharply extruded in space.

However, the separation of public andintimate auditory spheres along the soleauditory modality does not compare

with the sharpness and brutality of op-tical, thermal and acoustical isolationprovided by a wall. The remote creationof sound boundaries and the delimita-tion of intimate and public sonic zones

without walls are inherently complex anddifficult. However, within the context ofthis installation, a 12 dB gain proved

Fig. 6. Spatial sound effects: (a) illumination and shadow zones; (b) sound localization onreflecting surfaces. ( Philippe-Aubert Gauthier)

Fig. 7. Walls influence the sound localization. ( Philippe-Aubert Gauthier)

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432 Gauthier and Pasquier, Auditory Tactics

cally to participate in the collective andcultural understanding of the use of pri-

vate sound devices in public spaces[22].This positioning is at the heart of our ar-tistic statement and orients much of ourartistic work using technological devicesand knowledge.

Characterized by the separation be-tween sonic illumination and shadowzones and interaction with architecturalsurfaces, beamforming opens new av-

enues for spatial sound composition. Weare eager to observe and participate infuture developments of this promisingartistic project.

On practical and artistic fronts, there isa need for further exploration of interac-tion between the loudspeaker system and

various architectural spaces. Besides pub-lic spaces, concert halls and rooms usedfor electroacoustic or sonic art displayscould be stimulating sites for furtherexperimentation. Within the fixed timeframe of the Auditory Tactics residency,

we had only a glimpse of the possibili-ties. Hence, the stimulating future thatlies ahead.

Acknowledgments

Philippe-Aubert Gauthier acknowledges the supportof Sherbrooke City (Programme de bourses auxartistes et artisans dart ambassadeurs et en mer-gence). The authors thank Yann Pasco for his helpin the fabrication of the array. The authors acknowl-edge the support of Vidographe and the Pure-DataConvention 2007. This paper was produced usingopen source software.

References and Notes

Unedited references as provided by the authors.

1.Barry Blesser, Linda-Ruth Salter, Spaces SpeakAre

You Listening?(Cambridge: MIT Press, 2007).2.Blesser and Salter [1].

3.Vidographe invited us for a creation residency attheir PARC laboratory. Vidographe is a Montral-based art center devoted to independent videoand media art production and diffusion: , visited 25 July 2008.

4.Pure-Data is an open-source multimedia program-ming environment: , Pure Dataconvention, 2126 August 2007, visited 25 July 2008.

5.Philippe-Aubert Gauthier, Sound ReproductionUsing Multi-Loudspeakers Systems, Harvest MoonFestival, Concordia University, Montral, Canada,www.econtact.ca 7.2 (2004) and Philippe-AubertGauthier,Alain Berry, Wieslaw Woszczyk, Creativesound projection using loudspeaker arrays, Music-Works 93, 1416 (2005).

6.Philippe-Aubert Gauthier, Synthse de champssonores adaptative, Ph.D. Thesis, Universit deSherbrooke (Canada), 2007.

7.Yasushi Shimizu et al.,Dynamic sound image cre-ation by uni-directional sound beam reproductiontoward an interior surface with a DSP-controlled linearray speaker for Surround Sound Composition,Acoustics 08, Paris, France, 29 June4 July 2008.

8.Abraham A. Moles, lisabeth Rhomer, Psychologiede lespace (Casterman, 1978).

9. Barry Truax, Acoustic Communication (Westport:Abex, 2001).

3. Type of space investigated. Future pre-sentations would require carefulselection of an exhibition space,consideration of the position of thearchitectural surfaces relative to theloudspeaker array and the positionof the audience relative to the loud-speaker array. According to our ex-perience, spatial sound effects andperception with beamforming in agiven space are difficult to predict;

direct experiment is mandatory.4. Alternative spatialization settings. Afurther influencing factor on thereception of the piece is the com-plexity of the spatialization. It

would be interesting to reduce thenumber of beams to a single uniquebeam.

These are only some of the possibilitieswe envision for future versions of Audi-tory Tactics.

CONCLUSION

The conquest of sound space as a com-modity, possibly subject to personaliza-tion, privatization and merchandising,implies its division, its fragmentationand its specialization. Technologies andproducts such as Walkmans, MP3 playersand mobile phones all allow for a privatesound space to be superimposed on, orto override, the public sound sphere.This encourages the deployment andcreation of private auditory tactics ontop of or instead of public ones. How-ever, these technologies, along with thereshaping of the auditory tactics, bothserve and participate in an intrusive andpernicious agenda: reshaping privatesound as a commodity. Sound technolo-gies not only act upon social practices;they also stem from social practices anddesires [21].

With Auditory Tactics, we questionedthis fragmentation and superimpositionof sound spaces with the assistance oftechnological means. As such, the instal-lation offered a reflexive perspective onthis phenomenon through an artisticmedium. Beamforming technology wasfundamental in support of this artistic

proposition. We believe that such non-utilitarian, artistic and hacked use of newtechnologies must be pursued to allevi-ate the otherwise commercial, economicand technological determination of suchtechnologies identity. This is particularlythe case with a technological device thatas here is just making its way out of thelaboratory to become a socially absorbedmedium. Auditory Tacticsis also a culturaland political intervention aiming criti-

as far as 30 meters or as close as fewerthan 5 meters from the array. Whenlisteners were close to the array, the ef-fects previously described tended to de-crease: Sound seemed to come from thearray. A consistent array-listener distance

would be interesting to explore. As therelative distance increased, the perceivedrichness of the interaction between thebeams and the architecture increased:Sounds were localized as moving and

sliding on surfaces.Visibi lity of the array was detrimen-tal: When the loudspeaker array was

visually obvious, the spatial impressionof sound emanating from reflecting

walls was often annihilated. The humanbrain tends to combine vision of soundsources with sound localization (e.g. the

ventriloquism effect, the justi ficationfor the monophonic central voice chan-nel in sound for moving images [20]).However, subtle integration of the array

within the hall prevented many passersbyfrom visually identifying and localizingthe real sound source.

According to our own experience, thesound beams were also localized on ceil-ings, corners and other surfaces. In par-ticular, sounds projected by beams witha pivoting axis were clearly perceived assliding on the walls and corners. Themost intense effects came from very longsamples (without any drastic or repeat-ing onsets) that had a noise component:time-stretched breaths or drones. Asthe number of simultaneous sounds in-creased, the effect was reduced.

These results allowed us to identify sev-eral axes for future work.

Future AvenuesIn order to improve perception of thesound beams and to enhance the recep-tion of the installation, four axes needfurther exploration:

1.Simplification of the composition andsound material.What stems from theproject is the influence of the com-plexity and density of the soundcomposition on spatial soundperception and vice versa. Simpli-fication of the composition might

contribute to greater clarity of theacoustical beams as peculiar spatialsound entities. This is a matter ofthe attention and sensitivity of thelistener. For public space, it can beassumed that these are diluted.

2. Modifications of the loudspeaker array.It would be interesting to increasethe directivity of the beams and theintensity differential between illu-mination and shadow zones.

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Gauthier and Pasquier, Auditory Tactics 433

Manuscript received 9 February 2009.

Philippe-Aubert Gauthier is a post-doctoral fel-low at the Groupe dAcoustique de lUniversitde Sherbrooke, where he pursues research onsound field and sound environment reproduc-tion. Gauthier is a self-taught audio artist.His art and musical works have been presentedin Canada, the U.S.A., Mexico and Europe.

Philippe Pasquier is assistant professor at theSchool of Interactive Arts and Technology of

Simon Fraser Universitys

Faculty of Com-munication, Art and Technology (Vancouver,Canada). He conducts both a scientific andan artistic research agenda.

(Cambridge: Cambridge University Press, 2007), p.107125.

18. Philippe-Aubert Gauthier, Au-del des appar-ences on CD Cache 2006, Canadian ElectroacousticCommunity. Philippe Pasquier, Improvising Autom-ata in Catalogue of MOIS MULTI, 2005. PhilippePasquier, Metacreation: Machines endowed withcreative behaviors, IAT-847, Graduate course, SIAT,2008/2010.

19.Jens Blauert, Spatial Hearing (Cambridge: MITPress, 1999).

20.Blauert [19].

21.Sterne, p. 7 [10].

22.Selected terms and models of emerging technolo-gies fit the description by Steve J. Wurtzler, ElectricSounds(New York: Columbia University Press, 2007).

10. Jonathan Sterne, The Audible Past: Cultural Ori-gins of Sound Reproduction (Durham: Duke UniversityPress, 2003).

11.Blesser and Salter [1].

12.Sterne, p. 6 [10].

13.Sterne [10].

14.Lawrence E. Kinsler, Austin R. Frey, Alan B. Cop-pens, James V. Sanders, Fundamentals of Acoustic s(New York: John Wiley and Sons, 2000).

15.Beamforming is applied to emission and capturewith similar algorithms. Teutsch Heinz, Modal ArraySignal Processing: Principles and Applications of Acoustic

Wavefield Decomposition (Berlin: Springer, 2007).

16.Sterne, p. 15 [10].

17. Karlheinz Essl, Algorithmic Composition, in NickCollins, Julio dEscrivn (eds), Elect ronic Music

Nanotechnology, Nanoscale Science and Art

Leonardo Special Section

Guest Editor: Tami I. Spector

2011 is the International Year of Chemistry! To celebrate, Leonardo is seeking to publish papers and art-works that involve the intersections of chemistry, nanotechnology and art for our on-going special sectionNanotechnology, Nanoscale Science and Art.

Since its inception, nanotech/science has been intimately connected to chemistry; fullerenes, nanoputians,molecular machines, nano-inorganics and self-assembling molecular systems, all spring from the minds andlabs of chemists, biochemists and chemical engineers. If youre a nano-oriented chemist who is seriousabout art, an artist working at the molecular level, or a chemical educator exploring the mysteries of thenano world through the arts we are especially seeking submissions from you.

Published Leonardo articles that explore the intersections of nanotech/science and art include:Nanoscale and Painting by artist Filipe Rocha da Silva,Fact and Fantasy in Nanotech Imagery by scien-tist David S. Goodsell,and Midas: A Nanotechnological Exploration of Touch by artist Paul Thomas.

Interested artists and authors are invited to send proposals, queries and/or manuscripts to theLeonardo editorial office: Leonardo, 211 Sutter St., Suite 501, San Francisco, CA 94108, U.S.A.

E-mail: .

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8/11/2019 2010 Auditory Tactics: A Sound Installation in Public Space Using Beamforming Technology

9/9

Re-Imagining the Moon

Guest Editor: Sundar Sarukkai

Human exploration of the moon has become the subject of renewed interest, with upcoming space mis-sions from all the space-faring nations, as well as private companies. In late 2008 the Indian Space Agency,ISRO, launched the Chandrayaan 1mission to the moon.

The moon has profoundly influenced the human imagination over the centuries, in the domains of myths,religion, art and science. A variety of cultures have generated rich narratives about the moon. The moon ismore than a mere objectit is also an image, an illusion, a picture. It inspires stories about lunacy as well aslove. It has regulated our lives in a fundamental way by catalyzing calendars based on its movement. Storiesof navigation are incomplete without the shadow presence of the moon.

The engagement of poetry, art and literature with the moon has had a profound influence on these activi-ties. The moon also has a political significancenew space projects related to the moon by countries suchas Japan, China and India are fundamentally tied to the new articulations of what these countries are and

want to be.

The LeonardoSpecial Section Re-Imagining the Moon will remind us of this historical, cultural and sci-entific trajectory in which the moon plays an important part even as it suggests new, contemporary reflectionson the moon. The section aims to publish articles from a variety of disciplines and hopes to receive articlesthat explore various social and cultural aspects related to the moon as well as those that engage with therelation between the moon and the artistic and scientific imaginations. Reflecting the universality of thisinfluence, we seek articles from countries and cultures throughout the world.

We are also particularly interested in documenting artists projects connected to current space exploration

missions to the moon and collaborations between artists, scientists and engineers on moon projects.Deadline: This is a three-year project. Manuscripts will be considered on an ongoing basis until 2012.

Submissions: Send manuscript proposals to Leonardo, 211 Sutter St., Suite 501, San Francisco, CA 94108,U. S. A. E-mail: .

Authors are encouraged to submit a manuscript proposal before sending a full manuscript.

Author Instructions: .

The project is part of the activities of the Leonardo Space Arts Working Group: . The project follows on the Bangalore Space and Culture Symposiumheld in 2007, a collaboration of the National Institute for Advanced Studies, The Arts Catalyst, Leonardo/

OLATS and the Srishti School for Art, Design and Technology: .Sundar Sarukkai, trained in physics and philosophy, has a Ph.D. from Purdue University. His research inter-ests are in the areas of philosophy of science, philosophy of mathematics, postmodernism, phenomenologyand philosophy of art, drawing upon both Western and Indian traditions. His books include Translatingthe World: Science and Language(University Press of America, 2002), Philosophy of Symmetry(IIAS, 2004) andIndian Philosophy and Philosophy of Science(CSC, 2005). Currently he is professor and dean of the School ofHumanities and head of the Centre for Philosophy at the National Institute of Advanced Studies, Banga-lore, India.

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