Offener Schaltkreis. An Interactive Sound I catalogue-pd/27-Haag.pdf · PDF fileOffener...

Click here to load reader

  • date post

  • Category


  • view

  • download


Embed Size (px)

Transcript of Offener Schaltkreis. An Interactive Sound I catalogue-pd/27-Haag.pdf · PDF fileOffener...

  • Offener Schaltkreis. An Interactive Sound Installation

    Christoph HaagAcademy of Media Arts

    Cologne (KHM)Peter-Welter-Platz 2

    50676 [email protected]

    Martin RumoriKlanglabor, Academy of Media

    Arts Cologne (KHM)Peter-Welter-Platz 2

    50676 [email protected]

    Franziska WindischAcademy of Media Arts

    Cologne (KHM)Peter-Welter-Platz 2

    50676 Colognewindisc[email protected]

    Ludwig ZellerAcademy of Media Arts

    Cologne (KHM)Peter-Welter-Platz 2

    50676 [email protected]

    ABSTRACTOffener Schaltkreis (Open Circuit) [1] is an interactive sound in-stallation developed by students at the Academy of Media Arts,Cologne. It mainly focuses on openness, which applies to all facetssuch as optical appearance, the interface given to the user, the tech-nical tools being used and the collaborative style in which the in-stallation has been developed. In this paper, we will discuss theaesthetical and technical issues of our sound installation OffenerSchaltkreis.

    Keywordssound installation, interaction, interface design, tangible, pd

    1. INTRODUCTIONAt the Academy of Media Arts, art, technology, and science

    work together for mutual enhancement. Different ways of think-ing meet: theory encounters practical design, technological pro-grammes and artistic imagination combine. [2]

    The interactive sound installation Offener Schaltkreis is actuallya result of such a meeting of two different programmes within theKHM: Hybrid Space and OSFA.

    The Hybrid Space was founded by Prof. Frans Vogelaar withinthe media design department.

    A new interdisciplinary field of design, researching the trans-formations of architectural, urban/regional space of the emerginginformation age, explores the dynamic interaction of architec-ture/urbanism and the space of mass media and communicationnetworks. It develops scenarios for the interplay of public urbanand public media space. [3]

    The OSFA series of workshops introduced by Martin Rumori isconnected to Klanglabor within the department of arts and media

    Permission to make digital or hard copies of all or part of this work forpersonal or classroom use is granted without fee provided that copies arenot made or distributed for profit or commercial advantage and that copiesbear this notice and the full citation on the first page. To copy otherwise, torepublish, to post on servers or to redistribute to lists, requires prior specificpermission and/or a fee.Pd Convention 2007. Montral, Qubec, Canada.Copyright 2007. Copyright remains with the author(s).

    Figure 1: OSK at Makeart Festival, Poitiers

    studies. OSFA translates to open source for arts and emphasizeson all aspects for using open source technology for artistic pur-poses.

    Offener Schaltkreis is experienced by putting freely placeablespeaker-cylinders on a labyrinth created out of open copper tracks.Since these tracks carry electrical audio signals, correspondingsound layers become audible. This simple principle of operationis derived from another project, created at about the same timeat KHM: Talking Cities Radio [4]. While Talking Cities Radiois an interface for the audible content of an exhibition, OffenerSchaltkreis aims at being a sound installation whose aesthetical cri-teria were entirely developed collaboratively from scratch.


    2.1 Model of a cityIn a city the acoustic impressions differ from place to place, just

    like inhabitants and surroundings are different. Every neighbour-hood has its characteristics and on the way through a city, not onlythe visual, but also the acoustic environment is constantly chang-ing.

    Within this installation we wanted to strike emphasis on the pos-sible simultaneity of inhomogeneous enviroments. The juxtaposi-tioning of heterogeneous topoi through the simple arrangement ofaudio sources, as the translation of what inhabitants of a city faceon a daily basis. A heterotopia, not in a strict foucaultian sense,but as the coexistence and interference of places, in this case repre-sented through audio sources. The experience of a urban environ-ment gets downscaled and transferred into a room. An experiencewhich is not given, but dependent on the activity of the perceiverand his will to explore his enviroment.

    They wander through the sectors of New Babylon seeking newexperiences, as yet unknown ambiances. Without the passivity oftourists, but fully aware of the power they have to act upon theworld, to transform it, recreate it.[5]

    Figure 2: user interacting with Offener Schaltkreis

    Through putting the speaker-cylinder on the tracks a concreteplace of sound is created, which uses the copper as a source forits emission and therefore for its sensual manifestation. But thisconcrete place of sensual manifestation is not connected to a specialplace on the map. It is not static but in a permanent shift, just likeits audio source. Free positioning of the speaker-cylinder allows thevisitor to create her own soundscapes. Soundscapes, which openthemselves only through time and movement in space.

    2.2 Transporting audioThe system of copper tracks on the ground derives from the

    transportation networks of a city. This fact made it obvious fromthe beginning, to work with sounds and noises of the city, includ-ing their transformations and synthetic imitations. For every coppertrack an individual piece of sound has been created from collectedsound material.

    The installation is constantly playing. For every track a virtualread head loops in various speeds through a given sound piece. Ev-ery track includes four parts, which create, while playing all trackstogether, changing auditory scenes.

    2.3 The visitor as an authorA silent labyrinth created out of open copper trails on the floor

    carries the electrical signals of a multichannel sound repository.By putting freely placeable speaker-cylinders on them, the carried

    sound layer becomes audible. Offener Schaltkreis reacts dependingon the manner in which the speaker-cylinders are used: if noth-ing is moved, the sounds stay calm and soft, but if cylinders arerepositioned, the currently played sound material is modulated byincreasing speed, pitch and velocity.

    If nothing happens during a few minutes, the installation startscooling down, back to the quietest, lowest level, where it remainssleeping: just like every acoustic space sleeps while nobody isthere. As soon as a single cylinder is moved during this state, thesounds of all speakers suddenly jump to a higher level of activity.Thus, they give the impression of a social structure: a sensitive,pulsating, constantly shifting body, built with sound.




    Linux machine

    AD-DA interfaces /


    Copper floor installation




    t b b

    pd bounds



    s likiSave

    r likiSave

    r likiEvent

    s likiEvent



    t f f f

    r lb


    rohrWatcher 1


    r lb


    rack 1 rack 2


    10 to 50



    metro 30


    r lb


    e!ective slided


    s spMul

    expr ($f1 - 10 ) / 40 normalized to 0 - 1

    s volMul


    eg. globalSpeed

    take more if less visitors

    metro 2000

    expr $f1 * 0.6 + 0.1

    pd decrementor

    + 15 - 4

    moses 11


    expr $f1 * 0.3 + 0.03

    + 15

    moses 11

    + 6

    $1 2500

    rohrWatcher 2

    rohrWatcher 3

    rohrWatcher 4

    rohrWatcher 5

    rohrWatcher 6

    rohrWatcher 9

    rohrWatcher 10

    rohrWatcher 11

    rohrWatcher 12

    rohrWatcher 13

    rohrWatcher 14

    rohrWatcher 15

    rohrWatcher 16

    Figure 3: technical flow chart

    A Linux PC with a multichannel audio interface drives the openlyinstalled copper tracks (mass and signals). The freely movablespeaker-cylinders also have open copper contacts at the bottom sothat placing them on the tracks connects the amplified audio signalsto the speakers.

    3.1 SoftwareThe audio recordings described in chapter 2 are played back by a

    pd patch [6]. The patch is freely available at [1]. It reads the materi-als in progressing loops, playing repeatingly with forward-movingloop markers. That kind of macro-granular synthesis/sequencing

  • creates a diffuse sound, that morphs between different areas of therecordings, presenting ever-changing sound facets.

    The interactive mapping of the visitors activity to sound shapingparameters like volume, loop length (or macro grain length)and thus pitch and speed is done directly in each tracks playerinstance.

    The more the system is stimulated (up to a certain point), theless the actions of the visitors are taken into account. This kindof damping makes it hard to reach the defined maximum value,allowing for soft boundaries of the dynamic range. The lower endof the dynamic range represents the abovementioned sleeping.In this state, the least activity on the speaker leads to a sudden highincrease.

    In order to accomplish the interactive mapping, it is necessary totrack the visitors actions. Therefore discrete put and removeevents are generated based on electrical measurements on the cop-per tracks.

    3.2 HardwareBesides the actual audio content signals, all tracks carry an in-

    audible 20 kHz sine signal at constant amplitude. This is used as areference signal for counting the amount of speakers that are placedproperly on the copper tracks. The sum of the audio and the refer-ence signals is fed back into the corresponding adc~ inputs of pdwhere the 20 kHz sine is isolated.

    reference signal content signal sum signal

    + =

    Figure 4: signal compo