I decided to try out something new. Recently, I discovered an effect that I find quite interesting: From all work I’ve done so far, the ones that I made public as early as possible are the ones for which I get the most reactions. Also, posting to forums seems to be quite effective, whereas the usual scientific publishing method (journal paper, conference paper, book, etc.) are actually the ones, people tend to ignore.
In addition to that, I observed that none of my ideas where actually stolen by others (a common reason people come up with when it comes to spreading ideas). Having this in mind, I’ll try the following experiment: For one of my ongoing projects in tangible and auditory interfaces, I will ignore the broadly accepted policy to retain all information until it’s done. Moreover, I will try to present all relevant information on both the conceptual and the actual process on this weblog while it is happening. This is the first part. I’ll share all websites about this project on Delicious.
The Background: Emitting Structure-borne Sounds
| My first encounter with structure-borne sound was some years ago when I heard about an art piece by Laurie Anderson called The Handphone Table (Now part of the permanent exhibition at the Museum of Contemporary Art, Lyon). Back in 1979, she designed and built this resonating table, where visitors can lean on with their arms, connecting the table surface with their head via their forearm bones. Via this “sound bridge”, vibrations originating in the table travel through the bones to the jaw bones, where they can be perceived as stereo (!) music. As I never saw and experienced the table by myself, I have no clue how it sounded like. All I know are that there are some images of it on the net [Pasta & Vinegar, 2005 | Replay | etc.], and that she made a textual description: |
When the listeners put their elbows on the table and cover their ears with hands, they can hear the sounds coming through wood and bones of their own arms which, similarly to wood, have a porous structure.The principle of the performance of Handphone Table bases on the conduction of sound through bones. Stereophonic music in low ranges is strengthened and processed to the form of impulses, spread through metal bars connecting with four points on the inner surface of the table top. [Pasta & Vinegar, 2005]
On this webpage, there is also a conceptual drawing by her, showing the technical details of the system. Unfortunately, the image’s resolution is very poor, so it is difficult to impossible to read the accompanying text. Apparently, there is a more recent, site-specific version of the table that is set up in a rotunda in Sao Paulo and Rio.
When searching the net for this introduction, I re-found Touched Echo, an installation by Markus Kison that turns a balustrade into a sound-emitting object, quite similar to the Anderson’s Handphone Table.
The Background II: Listening to Structure-borne Sounds
There are many ways to listen to structure-borne sounds. One, I already explained in the previous paragraph: bone conduction. Another possibility of course is the transformation of the vibration into air compression, which in turn can be perceived by the “normal” hearing process. A third possibility is quite common in medicine: the use of a stethoscope as an amplifier/director for sound waves. For me, it is currently unclear whether the observed sound from a monaural stethoscope is perceived purely as air-borne, structure-borne, or as a combination of both. For examples of such monaural stethoscopes, see this list.
The Idea: A Vibrating Surface to be Used with “Stethoscopes”
Storyboard concept drawing
Now to the guts. The idea is now to build a table or a surface that emits structure-borne sounds that one can perceive and manipulate via custom-build monaural-stethoscope-like artifacts. Currently, I think of the manipulation of the sounds to be made by RFID tags and readers. You might get a better idea of what I’m talking about when looking at the schematic drawing. The first approach into this direction was to actually try to build a bass shaker out of an old speaker. For this, I disassembled an old subwoover and found a surprisingly small speaker in there. Looked pretty cheap, actually.
After some net-searching, I found some instructions for DIYing a bass shaker. I adapted this, to what I thought are my needs, and finally came up with this setup:
Basically, I removed the membrane completely (without cutting the wires which were attached to the membrane) and added an extension to the center part of the driver. Luckily, I have now access to a wood workshop, so I made use of this opportunity and build a custom “puck” that I glued on top of the dome-shape black part. Works pretty efficiently.
Unfortunately, the result of this system for the purpose of inducing (unhearable) vibrations into a surface (I took the next table I found) was not as I expected it, probably because vibrations that travel through wood are (a) either too small to be perceived by the bones, or (b) can also be perceived as air-borne sound waves emitted by the table. But I found a very inspiring effect (that is more or less totally unconnected to the original idea): When placing the speaker on top of a long and empty shelve (see also the first image in this post), you can create a sound shower, that emits sound not only from a single point above you, but from the complete shelve itself. That was a pretty nice experience.
Next Steps
For the next days, I plan to experiment further into the direction of sound-emitting surfaces. For this, I just ordered bass shakers.
Another investigation is to integrate a discussion I had with a colleague, an interaction designer, who is interested in computer supported work and innovation. But I’ll write about that in another post.