CymaSense: A Real-Time 3D Cymatics- Based Sound Visualisation Tool

Transcription

1 CymaSense: A Real-Time 3D Cymatics- Based Sound Visualisation Tool John McGowan J.McGowan@napier.ac.uk Grégory Leplâtre G.Leplatre@napier.ac.uk Iain McGregor I.McGregor@napier.ac.uk Permission to make digital or hard copies of part or all of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. Copyrights for third-party components of this work must be honored. For all other uses, contact the Owner/Author. DIS'17 Companion, June 10-14, 2017, Edinburgh, United Kingdom 2017 Copyright is held by the owner/author(s). ACM ISBN /17/06. Abstract What does music look like? Representation of music has taken many forms over time, from musical notation [16], through to random algorithm-based visualisations based on the amplitude of an audio signal [19]. One aspect of music visualisation that has not been widely explored is that of Cymatics. Cymatics are physical impressions of music created in mediums such as water. Current Cymatic visualisations are restricted to 2D imaging, whilst 3D visualisations of music are generally based on arbitrary mapping of audio-visual attributes. This paper looks at the design of CymaSense, an interactive tool based on Cymatics. Author Keywords Autism Spectrum Condition (ASC); Assistive Technologies; Music Therapy; Interactive Audio-Visual; Cymatics. ACM Classification Keywords H.5.2. Information interfaces and presentation: Graphical User Interfaces (GUI); Prototyping; Screen Design; User-Centered Design; Visualization Theory, Concepts and Paradigms. Introduction Sound visualisation takes many forms, which can be organised along a continuum, from pragmatic or functional to artistic [11]. On the functional side, volume unit (VU) meters (see Figure 1) exemplify 270

2 Figure 1: VU meter Figure 2: Cymatic image of sound vibrated through water Figure 3: Chladni plate representations which, though abstract, have become standard. In this case a VU meter provides an informative visualisation of loudness. Most software music players include a visualiser that fall on the artistic side of the continuum. The visualisation is driven by the audio data, but no information about the sound can be inferred from the visuals. Sound visualisation techniques can also be categorized in function of the semantic link between a sound and its visualisation. A recognised categorization is used in Auralisation, the discipline in which information is conveyed through sound: Auditory Icons [5] are linked to what they represent semantically. For example, in a user interface, the action of deleting a file can be represented by the sound of an object thrown in a trashcan. Earcons, on the other hand, involve arbitrary mappings between abstract sounds and what they represent [2]. Their meaning must therefore be learnt. It is difficult to apply the abstract/concrete categorization used in Auralisation to sound visualisation, for practical reasons: common sound analysis techniques used for real-time sound visualisation do not provide any information about the source of the sound. For example, a bird sound can only be represented by the image of a bird if the sound can be identified as being a bird sound. The only data available are generally limited to loudness, pitch and spectral data. Natural Sound Visualisation Audiovisual mappings Devising a natural visual representation of audio signals involves finding perceptually meaningful audiovisual correlates. Research into audiovisual correspondences has identified reliable mappings, such as: size to loudness, vertical position to pitch, visual brightness to pitch, visual repetitiveness to sound dissonance, texture granularity to sound compactness [6][7][13]. What visual objects these parameters should be applied to, for representation of sound, remains an open question. There are countless metaphors and systems, mostly using 2D Graphics, with an increasing number of sound representation using 3D and virtual reality [1]. Cymatics Cymatics are physical impressions of sound created in mediums such as water (Figure 2) or through particulate material on a brass plate [9]. They are the result of diffraction and refraction of sound waves created within the visualising medium [4]. Sound propagates in a spherical manner from its source contrary to typical 2D representations of sound waves. Cymatics until now have been viewed as quasi-3d patterns on the surface of water or on the surface of a Chladni plate (Figure 3). The appeal of Cymatics as a sound visualisation technique is two-fold. Firstly, they present undeniable aesthetic qualities (see Figure 2), which makes them an interesting proposition for artistic visualisation applications. Functionally, Cymatics are unique in that they are concrete representations of a sound. This does not mean, however, that they are necessarily informative. On the one hand, Chladni patterns can make an effective representation of pitch (see vibration patterns of a circular plate vibrating at 2434Hz and 3986Hz on Figure 4 and Figure 5 respectively). On the other hand, the pattern changes resulting from small spectral differences can be quite dramatic and surprising. These are, however, deterministic and are 271

3 Figure 4: Circular plate vibrating at 2434Hz Figure 5: Circular plate vibrating at 3986Hz Figure 6: CymaSense sample output used by some instrument makers to visualise the tonal qualities of their instruments. The aesthetic qualities, combination of predictability and surprise that Cymatic patterns exhibit, as well as the fact that they are physically accurate representations of sounds make them a fascinating sound visualisation paradigm. CymaSense A prototype was developed to experiment with and evaluate the potential of Cymatics-based sound visualisations. CymaSense is an interactive application that generates real-time 3D graphics, inspired by Cymatics, intended to encourage musical exploration through visual feedback. Given the complexity of the equations that describe the propagation of a sound wave in a fluid in 3 dimensions, a simpler Cymatics-inspired approach was chosen: high definition Cymascope images (see Figure 2) of individual frequencies were used as templates for the creation of twelve 3D Cymatic shapes, relating to each of the semitones within a musical octave. Figure 6 represents an image generated by CymaSense. Some of the properties of the Cymascope reference images have been preserved (translucence, symmetry) and new features were added: use of colour and particles emitted by the Cymatic shapes (Figure 7). Mapping The mapping between audio and visual attributes was based on validated associations presented earlier. The novelty of the visualisation paradigm also afforded experimentations with the less obvious aspects of the mapping. Amplitude to scale of Cymatic shape and particle size mapping amplitude to scale is commonly referred to in literature [12][18]. Pitch to Cymatic shape This is consistent with Cymatic shape behaviours observed. The 3D shapes created were inspired by Cymascope reference images (See Figure 7). Pitch to colour lightness - lightness of colour is affected by the relative MIDI note or audio frequency, thus implementing a pitch to lightness relationship, referred to in synesthesia and crossmodality literature [14][22]. The higher the pitch, the lighter the visual component is. This also aids in differentiating the same Cymatic shape over several octaves. Sound brightness to Cymatic shape surface quality colour is commonly associated with timbre in audiovisual mappings, but colour was used for other purposes in the application. Therefore, we decided to experiment with surface qualities as a means of representing the spectral qualities of a sound. The Cymatic shapes generated for a given frequency were modified using a 3D morphing technique as follows: the shapes of bright sounds were made to appear sharper, while dark sounds were transformed to appear more rounded. Implementation The application was implemented in Cycling 74 Max [3] for real-time audio and MIDI processing, and Unity for real-time 3D Graphics generation [20]. The Open Sound Control (OSC) protocol provides the data communication channel between the two environments. Consequently, the implemented CymaSense prototype comprises of: (1) an interface to control audio input 272

4 Figure 7: CymaSense shapes Figure 8: CymaSense user interface Figure 9: Audio input analysis and visual output for single or multi-user interaction (Figure 8); and (2) a separate output screen (Figure 6). The sound analysis process is represented in Figure 9: if a MIDI input is chosen, both MIDI data and audio data are analysed MIDI data can include note number, velocity, note on/off and bend. Audio data is analysed for its fundamental frequency, its partial (or harmonic) frequencies and the amplitude of the signal. Audio spectral analysis is carried out using the iana~ object, which is part of IRCAM s Max Sound Box [8]. The processed audio data is sent via OSC protocol [15] to Unity where it is analysed and triggers appropriate visual output (Figure 6). In addition to the implementation of the mapping presented above, the tool includes several options that allow the user to customize the visual output: for example, the default Cymatic shape and particle colours can be modified by the user. A mode in which random rotations of the shapes are enabled is also available. This is consistent with observations made on real-world Cymatic shapes created in water. Conclusions and Future Work Possible improvements One of the challenges of the implementation is to keep latency to a minimum and maintain a high frame rate. This places limitations on the computation that can be performed per frame. However, being able to generate Cymatic shapes in real-time based on physically correct equations, rather than predefined shapes would make conceptual and aesthetic sense. The mapping between the audio and visual parameters of the system may also be improved. The mapping presented in this paper is currently being evaluated. Applications Potential outlets for CymaSense include use of the tool for musical creativity within commercial environments from projected audio-visual art installations, through to virtual or augmented reality applications. Additionally, CymaSense could be used as a therapeutic tool. Use of multi-sensory environments to improve experiences for sensory impaired users, including those with Autism Spectrum Condition (ASC), have been previously identified [17]. ASC is a lifelong neurodevelopmental condition where people share some of the following features in their diagnosis: difficulties in social communication and interaction; problems in the use of language and verbal communication. Music therapy is considered an effective approach for addressing language and communication skills for children with ASC and provides a non-verbal means of communication [10]. Music therapists use technology within their practice to achieve a greater sense of agency and stimulate the senses of autistic clients. Previous work has demonstrated that use of shared interfaces in a therapeutic setting can enhance communication and social interaction for autistic clients [21]. CymaSense is currently being evaluated as a means of augmenting music therapy for people with ASC in an 8-week study. References 1. Florent Berthaut, Myriam Desainte-Catherine, and Martin Hachet Interacting with 3D Reactive Widgets for Musical Performance. Journal of New Music Research 40, 3:

5 2. Meera M. Blattner, Denise A. Sumikawa, and Robert M. Greenberg Earcons and Icons: Their Structure and Common Design Principles. Human Computer Interaction 4, 1: Cycling Max. Retrieved February 14, 2016 from 4. Cymascope.com Physics :: Cymascope Research. Retrieved December 30, 2015 from l. 5. William W. Gaver Auditory Icons: Using Sound in Computer Interfaces. Human-Computer Interaction 2, 2: Kostas Giannakis A comparative evaluation of auditory-visual mappings for sound visualisation. Organised Sound 11, 3: Kostas Giannakis and Matt Smith Imaging Soundscapes : Identifying Cognitive Associations between Auditory and Visual Dimensions. Musical Imagery: Ircam IRCAM Forumnet Max Sound Box. Retrieved March 20, 2017 from 9. Hans Jenny CYMATICS. The Sciences 8, 7: Ronna S Kaplan and Anita Louise Steele An analysis of music therapy program goals and outcomes for clients with diagnoses on the autism spectrum. Journal of music therapy 42, 1: Robert Kosara Visualization criticism - The missing link between information visualization and art. Proceedings of the International Conference on Information Visualisation, Mats B. Küssner Shape, Drawing and Gesture: Cross-Modal Mappings of Sound and Music Scott D Lipscomb and Eugene M Kim Perceived Match Between Visual Parameters and Auditory Correlates : an Experimental Multimedia Investigation. Proceedings of the 8th International Conference on Music Perception & Cognition: Lawrence E Marks and John B Pierce of Sensory Dimensions. Psychological Bulletin 82, opensoundcontrol.org Introduction to OSC. Retrieved March 17, 2017 from Richard. Rastall The notation of western music : an introduction. Travis and Emery Music Bookshop, London. 17. Kathryn E. Ringland, Rodrigo Zalapa, Megan Neal, Lizbeth Escobedo, Monica Tentori, and Gillian R. Hayes SensoryPaint: A Multimodal Sensory Intervention for Children with Neurodevelopmental Disorders. Proceedings of the 2014 ACM International Joint Conference on Pervasive and Ubiquitous Computing - UbiComp 14 Adjunct September: S.M. Smith and G.N. Williams A visualization of music. Proceedings. Visualization 97 (Cat. No. 97CB36155), IEEE, SoundSpectrum Inc WhiteCap Screenshots - highly reactive visuals for your tunes. Retrieved December 2, 2015 from hots.html#. 20. Unity Technologies Unity - Game Engine. Retrieved February 14, 2016 from Lilia Villafuerte, Milena Markova, and Sergi Jorda Acquisition of social abilities through musical tangible user interface. Proceedings of the 2012 ACM annual conference extended abstracts on Human Factors in Computing Systems Extended Abstracts - CHI EA 12, Mitchell Whitelaw Synesthesia and Cross- Modality in Contemporary Audiovisuals. The Senses & Society 3, 3: