hello there, this is Juan & Pablo, introducing our first ideas about the project to undertake in the forthcoming weeks.
The initial idea is to attempt the development of some kind of device/s based in the principles of bone conduction and tactile sound, in order to use them as interfaces for the perceptualization of data/sensory information.
CALL FOR COLLABORATION
we are completely open for anybody that would like to join us, even if maybe just for collaborating in any aspect of the project or trying to combine it with any other of the projects developed within the group. In addition, any help, suggestions and advise of any kind you may have will be very welcomed and appreciated.
Bone conduction is the conduction of sound to the inner ear directly through the bones of the skull, bypassing the eardrum. Tactile sound is the sensation of sound transmitted directly to the body by contact. We are interested in exploring the frontiers between acoustic and tactile perceptions and to examine if these principles could be used to receive sensory information non-perceivable normally. Being something quite unobtrusive but complementary with the rest of the existing sensory modalities, we find it as an interesting way of extending our perception, making use of this possibility of 'listening without ears' that we all possess, and which its not very known.
So far we have been researching a little bit about those concepts and compiling info about sound art projects. commercial products and existing technologies that make use of them. Those are some of the links with further info that we have found:
Wired´s article 'High-tech hearing bypasses ears'
forum thread on bone-earphones
bone-conduction speaker device paper
bone-phone (Sanyo) 
bone-phone (Finger-whisper) 
previous post in our 'extra-senses' blog with related art projects
WHAT TO PERCEPTUALISE / LIMITATIONS
In addition, we started to think about what would we interesting to feed through these devices, considering also both the limitations and possibilities we could eventually find out. In any case, the device will receive sound, so its likely that any kind of sonification or direct audification processes will have to be necessarily applied to whichever input we intend to use.
We also found differences between using direct bone conduction via transducers attached to the skull, and those attached to other areas. These differences include the perceivable frequency range, creating in areas of the body others than the skull a mostly pure tactile feeling, similar to what we would get using small vibrators.
Another issue is the possibility of receiving spatial information. In the case of bone conduction through the skull, the source of the stimuli seems to be inside our head, with no perceived spatial cues, therefore this would not be suitable for any input with crucial information that requires precise localization (orientation, navigation, etc) , but could work to sense something relative for example to the state of an environment. Regarding this, we think that maybe an hybrid device could be built, including a combination of both bone conduction through the skull and tactile stimuli in other areas of the body.
So, possible things to be made perceivable through this device coud be: any range of the non-perceivable electromagnetic spectrum, infra-ultrasound, magnetic/electric fields, movement, augmented reality marks... ¿? We are thinking about these possibilities and checking how to implement any of them, but so far the priority is to start to work in the device itself, since later different inputs could be connected to it to try them out, and probably more accurate ideas about what could work will arise when starting to experiment.
Therefore, first plans include starting immediately this coming week to find out how to build wearable bone-conduction/tactile small transducers... which electronic components are more suitable, etc... in order to have asap something to start to experiment with in practice.
Any specific info about this you might have would be very much appreciated, we found some possible solutions, but none of them really small, so this technical issue is still not completely clear for a pair of electro-dummies like us.
Frontispiece of John Bulwer's Philocophus' The Deaf and Dumbe Mans Friend. Printed for Humphrey Moseley, London, 1648. Note the kneeling man who is “hearing” music through his teeth via bone conduction.