learning the ropes

We want to be able to sense how far people are pushing the poles in our installation. I thought we could do this by measuring how much force the PVC poles are exerting on the ring they’re sitting in.

Since force sensing resistors from Interlink Electronics are expensive ($5-6/each) and also because I couldn’t see how the fragile FSRs would fit into the holes we planned to use, I wanted to find a better solution.

I discovered it was possible to create FSRs out of wire and plastic wrap. Others have used conductive foam and wire mesh. Reading about linear position sensors also gave some insights.

I took 22 gauge wire from the physcomp lab, stripped it, and bent it back and forth to mimic the “fingers” on the FSRs I purchased from Interlink. After making two wire finger pieces, I wrapped one in seven layers of plastic wrap. I place the second set of wire fingers on the outside of the package and wrapped it into the existing package. My first few tests seemed very promising. When no pressure was applied to the package, the resistance was infinite. When I squashed the package, the resistance dropped down to about 10K.

The next trick was to try to duplicate this behavior on the end of a PVC pipe. We first tried applying the plastic wrap/wire packages around the end of the PVC pipe. The results were less encouraging than my initial experiments.

The homemade sensors were unreliable: either the sensor package was too tightly squashed between the PVC and the surrounding hole (and gave no resistance) or it was too loose and no amoung of bending the pole caused a reading.

The Audio Art class will present a show of our work on the 9th Floor of the Tisch Building on Sunday, April 29th from 5-8pm. Email me for further details.

On Saturday, Shlomit and I built another prototype of our audio art installation.

We went to Home Depot in search of bamboo and springs, but came back with 1/2″ (ID) PVC and cast iron flanges.

The bamboo remains a cost-effective option ($1.79 for a package of 4-5 x 5′ stalks).

We attached 3/4″ x 1/2″ reducing adapters onto one end of ~5′ x 1/2″ (i.d.) PVC pipes and screwed them into a 3/4″ flanges mounted on a sheet of plywood. We painted the PVC poles hunter green to loosely reference a field of tall grass.

We created the prototype with two poles on it to see how the poles would flex as people move through them.

It was a great day to work outside and we were pleased with the progress we made.

Construction Lessons
- When cutting plywood, cut through the side you wish to display so the ragged edges are hidden
- Plan the flange installation better so the holes will line up on the top and bottom playwood pieces
- We will need to custom cut a 4′x8′ plywood sheet to get the 6′x3′ installation we want

Sound
We made further progress as we began to discuss the sound of the field. Both of us were drawn to the opening bars of Stravinsky’s Rite of Spring. The was some initial confusion about whether we were listening to the “Rite of Spring” or the “Firebird Suite”, but I resolved that as of this writing. The solo oboe (or perhaps clarinet?) provides a mysterious sonic backdrop for exploring a new space. We plan to edit a small sample from the first track and control its playback using the sensors we are planning to attach to the PVC poles. As users enter the installation, they will have the opportunity to push their way through our sound field. Each subsequent PVC pole they push will play the next piece of the sample we’ve chosen. If they walk push through the field at the right speed (according to the mood of the selected piece), they will hear the melody as they move.

Alice Planas and I have been investigating the idea of speech as music. The following is a summary of our in-class presentation from Friday, April 6.

Why?
- We’ve both done field recordings
- Alice interested in the creative potential in the raw content she’s been capturing
- I want to see what can be done compositionally with speech as a “generator,” for melody; many people seem to have musical voices

Process
- Tried two approaches initially: compositional & computational

- Attempted to write melodies from in-class recordings by listening and transcribing. This is time-consuming — and made further difficult by the distraction of the meaning of the spoken words. Perhaps it is easier when you don’t know the people who are speaking or don’t care about the content of the discussion… but in our case we were too close.

- Attempted to create a pitch-following patch in MAX/MSP. The idea behind pitch-following was to separate the frequency spectrum into separate slots – ideally a half-step apart and then track which slot had the greatest energy level.

Pitch-Following Resources
- Fiddle – MAX/MSP patch for continuous pitch tracking
- Paper: Strategies for Continuous Pitch and Amplitude Tracking in Realtime Interactive Improvisation Software
- My earlier experiments

Listening Selections
Larry Austin – 3 tracks audio portrait of Joan La Barabara (obtained at Avery Fischer Media Center in Bobst Library)
Joan La Barbara – 73 poems
Thomas Buckner – “His Tone of Voice at 37″
Paul DeMarinis – Music as a second Language:“An Appeal”
Laurie Anderson – “NY Social Life” (requires NYU ID/password)
Bobby McFerrin http://www.youtube.com/watch?v=LtXrKo8Btfc

Bertoia Sounds
- Clickable sound links on this page; these are rather bell-like sounds… clangy and mechanical, but they do have an interesting personality.

Bertoia Sound Sculptures
- An online catelog of sorts. Minimalist aesthetics.

Sonic Architecture
- Works from architects/designers Bill and Marv Buchen. Many are located around NYC.

Today we experimented with different strategies for sensing the motion of springs. The first was inspired by electric guitar pickups. I thought we might be able to create an electromagnetic pickup to sense the vibrations in the springs. We tried to create a simple electromagnet out of a nail and some transformer wire…. oh, yes… and a power drill.

We scrapped the pickup idea after measuring the resistance of the coil to be 0 Ohms. I was concerned it might short something out. Shlomit also thought we would have more creative possibilities if we used sensors rather than capturing the sound of the springs directly.

Returning to a previous sensing idea, we experimented with a flex sensors.

Flex sensors are not ideal for our application; they only sense motion in one direction and require a fair amount of deflection in order to produce a useful reading. (note for the future… measurement ranges would be useful for documentation purposes)

We also considered mounting the springs on top of a pair of joystick potentiometers to sense X-Y movement. The miniature potentiometer we tried to use for our prototype was too stiff to yield useful results. We wrapped a copper wire around the dial of the potentiometer, hoping that motion of the springs on our installation mockup would move the potetiometer and generate a varying resistance. No luck.

Another version of the musical speech patch. I spoke with Peter last week about fffb~ and made it work — to some degree.

I ran into trouble finding the frequency bin with the maximum energy. Jonathan Marcus helped me with a solution to that problem using the zl object.

The patch makes some sounds now, but still not what I hoped for. I wanted a patch that would highlight the musicality of recorded speech. I expect it would work better on some voices than others, but so far it just sounds “random.”

• When the .wav file is silent, the patch plays the last frequency in the frequency transform list (to fix, I will need to detect that case and turn off the cycle~ object)
• I tried testing the patch with the cycle~ object as an input, thinking that a pure tone would be a good way to test the patch’s ability to recognize frequencies. As I changed the frequencies of the cycle~ object going into the patch, there were some spots where the pitch detection “blew up” and returned to the highest frequency in my list.
• More experimentation needs to be done with voice recordings to see how they respond. I will post some results soon.

Using the patch
- Enable the DAC
- Click the “open” message to load a file into the sfplay~ object
- Click the “1″ attached the sfplay~ object to start playback
- The following controls modify the output: transform strength, wave volume, and transform volume
- “Transform Strength” controls the scaling of the values coming out of the fffb~. Increasing the transform strength with cause larger numbers to be packed into the frequency bin energy list. This primarily affects the height of the peaks on the multislider display.
- “Wave Volume” and “Transform Volume” adjust the relative sound levels of the original .wav file and the transformed signal. Set transform volume higher than wave volume to emphasize the transformed sound.

Shlomit and I made some progress on our audio art final. We decided to build a sonic field of springs.

Strategies for sensing movement:

• Flex sensor
• Magnetic pickup (like electric guitar)
• 2-axis potentiometer (joystick)

After brainstorming more about producing sound and sensing movement, we built a tiny prototype, using the technique I discovered while building a prototype for Designing for Constraints.

Aaron Siegel and Chris Peck and were guest lecturers in Audio Art this afternoon. Both compose works for untrained performers. This is one of the reasons I came to study at ITP. I want to design systems to enable untrained performers to collaborate musically.

Aaron’s piece “Work in Manufacturing” was a percussive piece with fixed rules, but varying outcomes regulated by each performer’s breathing. The rules of the piece made me feel disoriented at times because I had to keep a number of things in mind: how times I had inhaled or exhaled since beginning my current “station,” how many “stations” I had completed, and the number I had chosen as my “jump” number for selecting subsequent stations.

The overall sound of the piece was intriguing, but I prefer tonal music.

Chris’ piece “Worried Long” was a “choral” piece. I found it easier to appreciate the quality of the sound in this piece because it was richer and sustained. It sounded majestic as we sang it. I was very surprised at how harmonic it sounded — even though none of us knew the intervals we were supposed to sing. Further, only about half the class was musically trained. I don’t know how many of us could say that we know how to sing, but I really enjoyed the sound we created and would definitely consider it music. The dynamics were incredible and it was invigorating to belt out the slowed down lyrics with the rest of the class as we reached the climax of the piece.

I’ve been thinking about the discussion Amit and I had about believability. Both of the pieces seemed to have that quality. I knew nothing of the two composers beyond their remarks prior to performing the pieces, but it seemed that each piece matched the personality of its composer. Additionally, it was believable that we were creating the music together. Neither piece asked us to make an “impossible” committments in performing them. Collectively, we had all of the skills necessary to render the works. There was no need to think about which performers would be capable of properly interpreting their parts.