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EPresearchProject <br>
**Synopsis of Design Research**
This research has involved the design and manufacture of a portable floor, using modified loudspeakers to create the sensation of low frequencies in music from non-acoustic vibrational energy. The project has been driven by development of my previous research, which has explored the qualities of high intensity low frequency sound in music experience as well as my professional experience with low frequency noise issues in my immediate environment. I have aimed to explore the qualities of sensation in music experience and performance to contribute to this under-researched field. As less acoustic energy is required to create music sensation when using vibration technology, I hope to eventually use vibration systems to reduce low frequency noise issues and enrich the experience of amplified music.
My tests with vibration systems and large-scale audio systems have developed my understanding of approaches to using low frequency sound and where human perception crosses between what is heard and what is felt throughout the body. From this I have formed both an awareness of the capabilities and limitations of vibrational technology and an enthusiasm for exploring new applications for artistic use and development for non-music based installations.
**Extension of my research practise**
**The properties of music sensation and its significance in music experience**
My previous semester’s research explored the significance of high intensity low frequency sound as part of nightclub or dancehall music entertainment. Research this semester has developed further understanding, specifically looking at where audible sound merges with vibration sensation.
**Acoustic communication through to electro-acoustic communication**
I have been interested in the implications of vibration technology on communication through sound. Acoustic communication, specifically the relationship made between a performer and an audience, is effected by the means used to make sound. Electro-acoustic communication, observed as a performer, engineer or DJ playing through a sound system, has developed with the increased capabilities of sound systems, where generating high levels of low frequency defines qualities of music experience. This research explores the implications for vibration based systems on this aspect of electro-acoustic communication.
**Issues of lack of research on the subject and reasons for further exploration**
I have discovered that very little studies exist examining the properties of low frequency sound in a musical context. Research has overwhelmingly been from the perspective of sound as noise, from a detached clinical perspective.
The issue of lack of research on the physical experience of music has been presented in Discographies (Gilbert & Pearson, 1999). The authors trace a line in popular philosophy that has divided music into categories of 'the base' or physical, and 'the greater' music, that which appeals to the pure intellect or soul. This division and the undermining of the physical qualities of sound unpins broader views that ignore the physical aspects of music, which consequently has contributed to minimal research into this field. Contemporary thought on the subject has addressed sensation in music experience but most tests or quantifiable studies continue to address low frequency sound from the perspective of noise.
I am currently organising a series of tests with participants to evaluate how low frequency sound is felt in music, and where low frequency in music crosses from acoustic perception to being felt through the body. This does not aim to provide the level of detail provided by current noise-based research but does intend to place a technical understanding of low frequency sensation into the context of music experience.
**Key Questions**
**What are the qualities of sensation in music experience? How is this perceived acoustically compared with vibrationally?**
Experiments using a series of sound reinforcement systems and a prototype vibration dancefloor have been used to make observations that are contributing to my planned research tests. A large part of this research has involved the technical measurement of sound pressures and frequencies, analysis of the frequency content of tracks and feedback from friends and music enthusiasts.
My observations have largely been based on my own experiences and linking this to concepts of sound system design and measurement. I have avoided a reduction of results to the familiar, abstract descriptions of body sensation from audience members and approximations of overall sound levels as measured in clubs or bars. Instead I have focused on how sensation in music is perceived as being from an acoustic source compared with a direct sense of vibration from the floor or surrounding structures. This line of enquiry will aid in vibration system design.
Acoustic music sensation is determined by different sound pressure levels at varying frequencies. Often, these levels are well above what is considered safe for human hearing and. It is difficult to measure and record peoples’ experience of these aspects in the music entertainment environments that they are enjoyed. The tests I am planning will focus specifically on the ‘crossing-over’ between sensation and acoustic perception, while operating within recognised guidelines for safe sound levels. This will allow me to explore specific, quantifiable aspects of music experience while adhering to safe research practise techniques.
**What is the significance of vibration technology in terms of acoustic communication?**
**Between artists and audience**
Dancefloor vibration technology as a form of acoustic communication with an audience has a kind of perverse dynamic in its potential, with a strong relationship to power in sound. In increasing the bass, or sound levels generally, the operator forces acoustic preference on the listener. But without an awareness of the impact it has on the listener, the relationship dynamic is altered.
This can often be seen when the performer (typically a DJ) is behind the sound system, unaware of what the audience is hearing. Levels can be well above what is comfortable, particularly in high frequencies. When the DJ/performer can't hear most of the sound they are projecting, there is greater potential for a 'breakdown' in acoustic communication. The assertion of acoustic power on the listener is detached.
However, low frequency sound, because of its omni-directionality, can be felt and heard by the performer in much the same way as the audience. I believe that this aspect has a relationship to the importance of low frequency sound in amplified music performance. Without having a direct acoustic connection, an electro-acoustic connection is made more possible in the shared sensation of sound.
As a form of communication, a power relationship through sound can develop as a performer asserts their acoustic preference with electro-acoustic tools. I think that in the case of the vibration technology, as a communication tool that is not felt in the same way by both performer and audience, providing a performer with a vibration platform should be considered.
**Performance and artistic potential of vibration technology**
In tuning a system for low frequency representation that is not overtly perceived to come from the specific location of the floor, while reducing ‘overlapping’ acoustic low frequency information, an interesting presentation dynamic comes about. In tuning the vibration/acoustic system only the lower sub frequencies are filtered out from the acoustic system. When not standing on the floor, this reduction is not overtly noticeable, the sound does not seem to be lacking, or reduced. When standing on the floor, an increased richness and impact makes itself felt. The sound is more tangible and has a greater presence.
This for me relates strongly to both my experiences as a DJ and as an audience member. Performing to an audience allows for a particular form of acoustic communication, centred on a decrease or increase in the physical impact of sound. When a bassline kicks in, or extends lower and louder, a level of excitement is felt as part of the increased level of sensation throughout the body. In playing, an engineer of DJ can withhold a certain level of acoustic energy in reserve, increasing the level to reach a higher level of impact.
An interesting potential of the vibration technology hinges around the idea of being able to reserve the extra level of energy it provides to give an added layering of acoustic communication between audience and entertainer. The absence of the extra sensation is not missed, but when re-presented raises the impact on the listener. Some of the most effective performances not only use contrast in music, but also in the mixing or playing of music. A vibration system gives an extra layer for a sound performance that physically connects to the listener.
**Interrelatedness**
In Music as a Social Text (Shepherd, 1991) a concept of interrelatedness through sound is presented. In comparing hearing to other senses, Shepherd writes:
‘Vision, smooth and silent, stresses separation at a distance. It is the sense that allows us to inject ourselves into the world, to operate on the world over time and space…Touch is the sense basic not only to activating an awareness of ourselves, but also to making the fundamental distinction between us and not us. Sound, by contrast to both vision and touch, stresses the integrative and relational.’ (Shepherd, 1991, pg 159)
I am interested in the relational qualities of low frequency sound in terms of electro-acoustic communication.
Low frequency sound, due to its long wavelengths and high energy creates a form of shared experience, as everyone feels the same impact, swimming in the same sound. The direct vibration sensation, however, arrives at the body in a more direct, personal way. The sensation comes from a specific location, not from a source that is felt by all people in a shared space. Initially I felt that this would mark a reduction in acoustic communication between a performer and audience.
However, after attending a sound design seminar I began to think of this aspect from a different perspective. In designing sound systems or setting up sound for a room, the acoustic designer aims to give people the same experience, not largely affected by location. This is hugely problematic and sometimes impossible given the issues created by standing waves in a room, phase cancellation and other acoustic aspects. If a designer can create a uniform low frequency response, they are offering a homogenised experience of music. Specifically, the performer/engineer is reaching all people equally, communicating through sound evenly with wider reaching impact.
The dancefloor vibration system allows for a more uniform response, a greater coverage potential for the engineer, in theory making greater, wider impact and satisfaction for a larger audience. Potentially, this makes for a more integrated experience for audience members by avoiding the acoustic irregularities presented by low frequency sound. Whether this makes for a more integrated, relational experience for audience members is yet to be explored.
**Processes and Techniques**
**Manufacture of the dancefloor**
I have completed a prototype model of a vibration dancefloor, using modified loudspeakers provided by Pia. A significant part of my research has been into the construction of the floor as well as the tuning of the driver components and its integration into an acoustic system.
The dancefloor was initially constructed from a 1.2m x 0.6m 12mm MDF board, supported by two beams sitting on plastic feet. This initial design was chosen after consultation with Mike Xie, from the engineering department at RMIT. It forms the basis for more developed designs in progress that allow for greater tuning options and flexibility with different drivers.
Initial tests were conducted with aura exciter units (a low frequency shaker) from jaycar, with unsatisfactory results. The units did not have sufficient power handling or frequency response.
Installation of the units supplied by Pia provided much more satisfactory results, allowing for an exploration of placement and load dampening variables. Initially I found that the drivers produced a lot of noise at high frequencies, and were inefficient at lower frequencies. In response to this, I manufactured ‘straps’ made from cable ties around the units, and dampened their response by placing more load on the drivers with felt pads placed in front. This increased their efficiency at lower frequencies, while reducing noise. However, overall efficiency was lowered.
A large part of the research has been on the integration of the dancefloor into different audio systems, testing various loudspeaker configurations, crossover points and slopes, time offsets and compression variables. I have used combinations of analogue equalisers and crossovers, digital system controllers and passive and self powered loudspeakers and subwoofers. Tests have been conducted at Warehouse Sound Systems. The setting configurations chosen have been informed by my personal impressions of system performance, as well as those of my colleagues and friends.
After preliminary tests I have explored the role of shock absorption on vibrational efficiencies. I have consulted with Embleton’s, manufacturers of vibration isolation and shock absorption systems. My aim was to obtain a series of different vibration mounts to test both the reduction of vibrational noise and any effect on the efficiency of the vibration through the body. I initially planned on using springs because of reduced dampening, but chose to purchase rubber shock mounts because of safety reasons and difficulties in calculating spring loading variables.
I found that the change to rubber isolation feet improved the vibration characteristics of the floor, particularly around its edges. Vibrational energy builds up throughout the support beams as the dampening of the floor is reduced. Because of the increased efficiency I was able to conduct further tests on the comparative qualities of different driver mounting positions, and dampened or un-dampened drivers. In addition I added a crossbeam, aiming to more evenly distribute vibration across the floor.
**Tests with human participants, ethics application and system tests**
The limitations of the available technology, difficulties in measuring and observing the qualities of low frequency sensation in a nightclub environment and the clinical nature of existing research into low frequency sound has prompted interest in conducting tests with human participants.
A significant part of the research this semester has been in preparation for these tests, planned for mid-November. I aim to outline the frequency ‘crossover points’ where a direct vibration system can be utilised without detrimentally affecting the qualities of music experience.
In order to create low frequency sensation through acoustic means I need to employ high sound pressures. To conduct tests in a way that won’t damage the hearing of participants I have chosen to use Workcover guidelines to inform my evaluation of test sound systems.
These guidelines have required calculation of safe sound levels for different time exposures and frequency content and the use of appropriate sound measuring equipment. Consultation with Peter Dale (RMIT Acoustics) has assisted in forming a testing methodology that is both safe and retro-observable. I intend to use equipment from his department for later tests.
I have tested multiple combinations of sound systems to find an ‘acoustic reference’ to compare with dancefloor generated vibration. Sound systems at Warehouse Sound Systems and Rent-the-Rig Hire have been measured with sound pressure level meters to indicate safe operating levels and results have shaped my approach to final testing.
The eventual system functionality will be effected greatly by room acoustics and I have been studying basic acoustic principles for the prediction of room acoustic interference. These calculations will assist in system setup and measuring protocol to minimise colouration of sound from room acoustics.
The choice of different music test tracks is determined by the frequency spectral content of the pieces. This has been achieved by using spectral analysis software to measure and choose test tracks.
Application for ethics approval has required a structured approach to the tests and has necessitated a formal application process. I have currently been approved for a Level 2 classification with minor amendments, which have been submitted.
**Outcomes**
I have tackled several technical issues relating to the manufacture and tuning of the dancefloor. From this I am gaining an understanding of the many facets involved in vibration system design and the relationship between them. While the initial product is crude, it has allowed exploration of several tuning parameters and each ‘upgrade’ has assisted understanding other aspects of the floor design.
The system has allowed me to explore the ‘crossover point’ between hearing and feeling. Results have been variable according to sound levels and frequency content of tracks, with the two senses merging into each other in a difficult to qualify manner. This shifting of sensory perception is a fascinating aspect and hopefully the planned tests will broaden my understanding and later designs.
The magnitude of audio equipment required to create a decent level of bass sensation has illustrated the potential for vibrational systems in music entertainment. A part of my system tests has been ‘chasing’ a level of bass high enough to create very low frequency sensation and results illustrate that few sound systems extend to these frequencies.
The currently employed technology has placed limitations on sensation levels, in part due to a relatively high noise level from vibration artefacts, as well as limited power capabilities. However, they have allowed a specific understanding of the role of the floor itself as an ‘instrument’ and how its tuning effects sensation. Development of this line of exploration will require research into the resonant properties of various materials and greater understanding of vibration engineering principles.
I have gained a much more technical understanding of approaches to sound testing, adherence to safe guidelines and various acoustic calculation processes. The development of these skills has unpinned the design of the dancefloor and will assist in later design decisions.
During spectral analysis of tracks chosen from my record collection I have observed a pronounced sub-audible ‘hump’ with audible low frequency harmonic interference occurring as a result of turntable resonances. I believe that this interference leads to the ‘colouration’ that characterises a turntable’s ‘warm’ sound. However, this has interfered with the analysis of tracks for test selection and is currently unresolved.
An interesting issue of leg fatigue has also come about from tests. After standing on the floor for some time a sense of tiredness throughout the legs can creep in. I haven’t been able to specify this to certain frequencies or amplitudes but I believe that it is pronounced only at higher frequencies, ones that would be filtered from the floor for acoustic reasons. This however should be the subject of later tests and evaluation.
In preparing for tests with people my approach to final questions and methodologies has changed significantly. This has been largely dictated by the sound level guidelines that I am adhering to and the limitations this places on testing protocol. However, in doing this I have been able to focus on a very specific aspect of sound experience, hopefully resulting in more tangible conclusions.
**Further Questions and Developments**
A line of questioning that has arisen from this research regards the potential artistic applications for a vibration system. The role of a vibration system as an enhancement of music experience has interesting potential in the way that it effects a person’s perception of the space that they are in and how an audience experiences that space.
With the ‘point of reference’ of a stable floor becoming modulated a personal sense of the surrounding space also becomes transformed. I am unsure how to articulate this sensation modulation but I believe it corresponds to experiences of disorientation that I have had at large scale dance events where there is significant bass sensation coming from the floor. The sharp contrast felt and sense of stability regained when stepping off the vibration floor points to the wider sensory effects of body vibration. I am interested in non-musical artistic applications of this aspect, to transform a space or sense of space through frequency modulation across an area. In particular, the sense of movement in the body made by different ‘tunings’ of the floor point to the possibilities of structural instrumentation, activated by shifting audio frequencies.
The shared experience of low frequency sensation, evenly presented on a larger scale through a vibration system gives a sound designer greater control over the audience’s experience of sensation. After overcoming aspects of the technical challenge of even bass coverage, the entire dancefloor could be modulated, with different areas providing shifting levels of sensation. The potential for a sound engineer to dynamically create sensation changes throughout the audience and how this affects the group experience of sound is an aspect that I hope to eventually explore.
I hope to access specifically designed vibration technology for later research and to further develop dancefloor structural designs. My experience from this research has improved my understanding of design and I intend to continue consultation with engineering and vibration specialists for later projects. Integration into existing and new architectural spaces will be a later development of the project and will require continued consultation with architectural designers.
Direct vibration systems have opened the possibility of adding a sub-audible layer to music composition. I am fascinated in exploring composition possibilities for infrasonic vibration and intend to explore the role of sub-audible environmental vibration on people as a reference to composition approaches.