Mediate

Vibrotactile Progress

Touch/Vibration Context
Useful Equipment
Surfaces and 3D Forms
Considerations

Touch/Vibration Context

• Touch/Vibration most under-developed in a creative sense.

  Of the external actions upon the 3 senses, Sound, Light and Touch/Vibration, engaged for expressive creative uses by Mediate, the last is the most unknown and under-developed. Creative sound in the form of music has been with us for thousands of years. Creative light is newer, accelerating dramatically with the technological generating and controlling of electricity, although live movement and costume has probably run roughly in parallel with music and started even earlier. Touch has always been a fundamental communicating method of the human animal but creative vibration was almost impossible before electricity and, even then, there are next to no examples yet of actual 'creative' use.

• Most early experiments directed negatively (destruction, industrial injury).

  Vibration, acting upon the human body within the most useful range from about 4Hz to 500Hz, has usually been examined in a negative way: that is to say, for its destructive power [Gavreau, Tessler, US Army] and research focussing on its harmful effects in industry such as white-finger, back problems and other associated manifestations of machinery interactions with workers [Institute of Sound and Vibration Research, Southampton]. Airborne vibration, in the infrasonic and lower sonic ranges, can be extremely dangerous.

• Some positive experiments (mechanical structures, therapy).

  Vibration, examined and used in a positive sense, has been mainly for diagnostic and test energy applied to mechanical structures, therefore for long periods of time with minimum variation of frequency. Some early experiments were also made in the field of therapy.

  

• Decision to focus on vibration as if slowed-down music.

  We wish to concentrate on direct and very localised vibration, articulated and paced like slowed-down music and applied to various suitable parts of the human body, as part of the interaction dialogue between the other 2 senses and the subject.

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Useful Equipment

• To deliver non-destructive vibration.

  This comes in the category of 'transducer': a mechanism that converts energy from one form to at least one other. An audio loudspeaker is a good example: from electrical oscillations, it produces sound efficiently and vibration inefficiently. In industry, vibration equipment is usually termed 'shaker' to set it apart from the 'vibrator', used for personal stimulation. Shakers can be in any size, with relative power, from a small teacup to a large car. They can vibrate objects as diverse as eggs, fruit and aeroplane wings and are designed to work very efficiently for long periods. It seems inevitable that they too are only partly efficient: at higher frequencies, roughly above 100Hz, particularly due to their being attached to a surface or object, the combination tends to produce unwanted sound.

  The main mechanical forms of shakers are:

  • Hydraulic.
  • Pneumatic.
  • Electric Motor (with eccentric spindle or 'cam').
  • Electro-mechanical: coil and armature.

Many types eliminated (messy, noisy). For MEDIATE, visits to manufacturers revealed that the Hydraulic, Pneumatic and Electric Motor types were too messy or noisy. We also conducted experiments with MIDI-controlled eccentric motors and found many problems with construction, noise and flexibility of articulation (see example left).

Electro-mechanical suitable, particularly Inertial. The Coil and Armature type offered a good range and flexibility. Of this last type, there are two main designs: Normal: fixed/anchored body - moving armature (attached to object). Inertial: inertial/floating body - moving armature (attached to object). The first was not really suitable, since any pressure applied to the armature of a necessarily smaller model by part or whole of a human body would inhibit its movement and burn out the system. The second was ideal but expensive.

Cheaper source (toys / games) - extract driver. Early on in the investigation, two other lines of uses of semi-articulated vibration were identified: Medical. There are several generally available units that are either applied to the body to massage specific areas, or sat or lain on for relaxation. The vibration in both these types is not usually much articulated, but simply held at a constant, or with two or three set speeds. However, the mechanisms are interesting to us.

Toys/Games. As part of the need to make computer games more 'real' and interesting, crude jackets/waistcoats and chairs have been designed to give the wearers/operators kicks and vibrations in parallel with screen 'hits' and explosions. The electric drivers in these units follow the previous industrial pattern of motor and coil/armature, but cheaply produced with consequent lower power-handling coupled with some irregular fluctuations of dynamic output, the latter not being critical for the use.

Testing cheap unit A selection of these units has been bought and some of these drivers are being tested. Since they are so much cheaper, by a factor of up to 50, we are in the process of thoroughly evaluating their performance. In the micro range, work has started on investigating and developing the natural electrical property of piezo-electric material to physically oscillate when an alternating current is fed in. This could be useful for surfaces to selectively and accurately tingle to the touch.

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Surfaces and 3D Forms

As vibration experiments proceed, so do examinations of the following surface properties: Surfaces that successfully impart vibration: an evaluation of materials such as wood, plastic, metal and stretched skin/membrane (vinyl LP see above). Positions of shakers on surfaces relative to dead- and hot- spots. Surface textures, including electronically-controlled changes.

Sensory detecting surfaces (sensor activators being tested above). Similarly, 3D forms that can both impart and receive vibration/touch signals are being investigated. These include knobs, balls, handles and bowls.

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Considerations

• As the research continues, observations are being made on the relative sensitivities of human body areas:
  • Different attributes
  • Skin / nerve sensitivity
  • Bone conduction

  Related to this is the debate about whether to design settings that force the human body to take up a set position so that fixed sensory areas can address known body areas or whether to allow the body to assume any position and have the 'intelligent' control system find and address the body areas.

• Since sound is a by-product of the higher frequencies used in vibration, or even from the higher harmonics of lower frequencies, it is particularly unwanted in our multi-sensory environment since it clashes with the controlled sound as one of the other sensory experiences. Methods of surface control such as 'damping' are being investigated. If sine waves are used, there is minimum high-frequency content, but the vibration effect is necessarily smooth. If a 'spiky' waveform is used, this contains higher harmonics but gives a more defined jab or roughness to the single vibration. So consderation is being given to:
  • Frequency -v- efficiency (unwanted sound by-product)
  • Intensity levels
  • Sequences and rhythms

  A system of intensity (volume, level) calibration is being evolved. At present, the three categories are:

  • just feeling (lower limit).

  • pleasant (middle of range).

  • unpleasant (upper limit).

• A range of sensors is being evaluated, both for the specific needs of Touch/Vibration and for the suitability of inclusion in the overall environment sensor bank. Evolving out of these are action/reaction models which will lead to Interaction Models, both within the specific field of Touch/Vibration and as part of the whole environment of interaction between the three senses and the individual.

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