Note: These guidelines refer to the tactile sound workshop that will be held in Darmstadt during the 2014 Summer Courses (August 2nd-16th). This article may be updated now and then, so come back from time to time. The call is available at the IMD website. Deadline for sending the material: July 15th, 2014.
Update June 17th, 2014: New blog post “Spectral and vibration response tests on wooden planks“
The project consists of a chair with eight vibration speakers attached. The contact speaker model is Mighty Dwarf 26W.
These speakers will stimulate the tactile perception of the audience in eight distinct parts of their body. The chair will be presented as an installation, and people will be able to sit on it one at a time. The music will be experienced mainly through the body; however, the full range of the spectrum is audible. Two vibration areas will be on the back, two under the seat, two on the arm rests, two under the feet. The eight speakers are therefore coupled in four left/right pairs. These renderings hereunder provide an overview of how the final construction may look like (I used a Google Sketchup model, the actual chair will be different). You can see the placement of the eight speakers, but the cables are not visible. Each speaker has an input cable coming from a dedicated (mono) amplifier.
PRODUCING THE FILE FOR PLAYBACK
The 8-channel wav or aiff files will be prepared according to this channel scheme:
- Back, L
- Back, R
- Armrest, L
- Armrest, R
- Buttocks, L
- Buttocks, R
- Feet, L
- Feet, R
It must be a single file, containing the 8-track package.
The whole audible spectrum is covered, however the frequency response is not flat at all. A test has been made on a wooden chair. I used a 10-minutes sine wave sweep from 0 to 6000 Hz.
These test is only meant as an orientation, as it would differ according to the different chairs used and the different placement of the contact speaker.
In this video you see the Dwarf speaker attached to the seat of the chair. This video was made to let you hear how the sine wave sounds on the chair. You can see the frequency in real-time on the computer display. SR: 192000 Hz, Edirol FA-66 Mic: DPA 4006-TL at 50 cm from the chair (click here for the mic’s diagrams).
Here you see how the mic was placed:
An analysis via Audiosculpt shows the following spectrogram (general and zoomed views).
The perception of the vibrations on the body has been tested on the same chair, with the same sine wave sweep (see previous paragraph).
These values are only meant as an orientation, as they will differ according to the different chairs used and the different placement of the contact speaker.
- from 7 Hz, the vibration starts to be perceived (p) ;
- 16-35 Hz: more consistent perception (mf) ;
- 35-67 Hz: dramatic increase (to f);
- 57-65 Hz: peak (ff);
- 65-110 Hz: decrease (to mf);
- 110-130 Hz: slight increase, peak at 13 Hz (mf);
- from 130 Hz: slow decadence, with a small peak at 260 Hz and disappearing after 300 Hz (p – pp).
The idea is to use the spatialization of the tactile sensation on the body of the listener.
Different categories of spatial characterization can be analyzed in the pieces:
- Solo Vs. Tutti
- Left Vs. Right
- Up Vs. Down
But note that crossfading the signal between two or more points would not probably give the sense of a smooth transition in the space. Therefore, think in “blocks” or voices.
Other explorable territories are:
- Pulsating sound becoming continuous and back; rhythm/pulsation Vs. continuous sound;
- Polyrhythm Vs. Isorhythm;
- Dynamics, Crescendo and Diminuendo;
- Relationship between vibrating gestures (7-250 Hz) and audible-only gestures (over 400 Hz);
- Music for deaf people.
- Tactile sensations: granular, smooth, sharp…
Sound sources can include synthetic sounds and concrete material, but keep in mind that the frequency response of the chair will filter the sound and make some frequencies resonate way more than others.
The participants at the workshop in Darmstadt will have the chance to get acquainted with the construction, discuss, experiment, and tweak their pieces in order to adapt them to the actual tactile sound chair. The pieces can also be expanded in length if needed. The final compositions will be presented in a playlist before or after key-concerts and events in the frame of the Darmstadt Summer Courses 2014.
Please bring your laptop with your favourite multitrack audio editing software.
You can address specific questions to: touchmysound[at]alessandroperini.com