Tex-taal

Bharatanatyam is the oldest form of Indian classical dance form. It is performed on classical Indian music called Carnatic music, where immense significance is given to the music beats, and rhythms (taal and laya).

Ghungroos (an accessory worn around ankles with tiny bells on them) are a significant part of the dance form, as it largely contributes to the dialogue between the music beats and the dance steps. When an artist is performing Bharatnatyam the force and mp4ement of the feet as per the beats echo through space and is accentuated through ghungroos.

In numerous Indian cultures, tools, mediums, arenas associated with whether performance, or work, are considered auspicious and are often worshipped. Musical instruments are cared for with reverence, new machine or equipment in a house is often blessed before using, vehicles used for commute are also blessed in certain parts of India, and similarly with business books as well. Same is the case with ghungroos, where they are offered to the artist by their teacher (guru) after years of practice and dedication to the art form.

Just as tools or accessories are worshiped, so are the arenas. In Bharatanatyam, there is a tradition of bowing down to the ground on which you are performing before and after the performance, to apologize for stomping and dancing on it.

a namaskar in Bharatanatyam performed before and after the performance

How to address this emotion and the conversation of caring for the arena between the performer and their arena?

Textile speakers have this beautiful quality of being intimate and soft, like a gentle whisper. What if the performer’s feet whispered to the ground instead of communicating through fierce steps?

Ghungroos embedded with soft speakers

Turn on the sound

Find the process documentation here.

Initial questions:

• How will the sound react to the mp4ement? Will it be a change in volume or a change in soundtrack itself?
Going along the lines of original *ghungroos,* a change in volume sits well. It will be less confusing to the ears, and might be easy to comprehend.

• What microcontroller and other components to use?
Microcontroller: Teensy 3.2 with monoAmp and Audio shield is something that is flexible to have variations in soundtracks, with decent amount of online resources available to help explore and debug if needed. But it also requires a lot of components to be comfortable for a soft interaction. For the sake of familiarity with Teensy, let’s start with this one.

• What will the sound be?
The audio shield has in-built sounds, so maybe those or actual sound of the ghungroos.

• How will the mp4ement be tracked?

- Pressure sensors that track the impact of the dance steps
- tilt-contact circuit that can record mp4ement (in a binary manner)
- accelerometer

• What will the form of the e-ghungroos be (Dimensions and Materials)?

- Materials- to be determined after testing different combinations of speakers and their sound qualities
- Dimensions- as close to the original ghungroos as possible for comfort

• How will the interaction be? Will the two feet coordinate? Will it be a live feedback or a delayed one?

- Can the two circuits in the two feet communicate wirelessly?
- Can they predict mp4ements or record and store mp4ements that can be played afterwards?

• What to do about the chunky magnets!?

Explorations and Testing

1. Testing the sound and variable volume

Working with audio with Teensy 3.2 and the audio shield is complicated, is a gross understatement. After spending hours trying and testing out the Teensy audio tutorials ➚, it was still impossible to vary the volume. The example ➚ that shows the use of volume did not work even with a fixed predefined volume level, much less a variable one. Thanks to the nice people on this forum ➚, I was able to figure out that while using the monoAmp, I need to use something called mixers and gains, and build part of my code through Teensy Audio System Design Tool ➚. Needless to say, I was pretty proud to have figured out the most basics of code after spending over five hours into research.

varying the volume using a potentiometer

Materials:

• Teensy 3.2 + Audio Adaptar (RevC) or Teensy 4.0 + Audio Adaptar (RevD)

• MonoAmp

• Speaker (or a conductive coil + magnet)

• Potentiometer (or a variable sensor for input)

• conductive yarn (or connectors such as jumper wires or alligator clips)

• Battery equivalent to 3 V should suffice

Speaker circuit for variable volume

2. Testing the mp4ement-tracking using pressure sensors

While the circuit and interface were pretty simple, the interaction did not feel satisfactory. There was still the question of feet-to-ground impact being the main trigger. And as a performer, it just feels uncomfortable to have the pressure sensors attached to the feet.



However, I do wonder about the ground itself being the input sensor. The the concern here is to connect the ground sensors with the feet wirelessly so that the performer can actually perform, and not be tied to a place. There is also the question of needing a large number of input pins.



3. Considering the mp4ement-tracking using tilt sensors

Tilt sensors have a similar concern of the mp4ement needing to be highly animated and fierce, the opposite of what I am trying to address.

4. Testing the mp4ement-tracking using accelerometer

The thing I am least happy about is that this is another component added to the already long list of physical computing components (Teensy, audio shield, monoAmp).

The thing that makes this option more desirable than the other two is that this tracks the mp4ement, as opposed to the impact. And since the ghungroos have padding, one more hard component might not be the worst thing. (It certainly is not something I am happy about either).

Since I have not used accelerometer with a microcontroller before, I decided to just test the basic workings. Once more, some other nice people operating this channel ➚ helped me with the accelerometer testing, as well as calibrations!


accelerometer generating serial communication

I could not get a hold of Teensy 3.2 in time, so I will be using Teensy 4.0 and corresponding audio shield.

5. Testing the variable volume based on accelerometer input

This went pretty smoothly, even after shifting from Teensy 3.2 to Teensy 4.0 with the audio side of the code. It also made me think of the connections between the audio shield and the teensy 4.0.



So, here we have the final circuit on a breadboard.



The soft circuit

6. Considering the dimensions and form

How about sticking to the form and dimensions of the original ghungroos?
Why?
Because:

• It is a proven comfortable form for a dancer to perform with.

• It has affordances of padding- an extremely beneficial attribute considering the frustratingly large number of components needed to build a speaker

• The size is pretty similar to the breadboard above, and might just fit the components successfully.

7. Materials

While the electrical components of a circuit aren’t something that are easily available around a house, the textile materials most likely are. Tex-taal is brought to you solely by the fabrics found in my room and my wardrobe, retrieved either from unused clothes, worn out curtains, broken bags, or torn tents.



Materials for soft speakers
In order to decide the materials for the soft speakers, I first need to understand what kind of sound is produced by speakers made from different materials, hence, I decided to build a soft speaker library (or at least start one).

Now, countless combinations of conductive materials, fabric substrate, and coil patterns are possible, and I needed to narrow down the scope. Since the size of the ghungroos is more or less fixed, and relatively small, I am eliminating the options of conductive tape and fabric, since conductive thread can create comparatively intricate and petit patterns.

As for the size, based on the space available along with the components to be fitted, an area of 1.2” to 1.5” will be available for the magnets to occupy.

With silver, steel and copper conductive threads available, and a variety of fabric bases, I decided to start with making a same size speaker with same number of coils for all the combinations to test with to eliminate the variations due to variables.


Soft speaker library with leather, wool, cotton, polyester base fabrics in plain and twill weaves

Denser and stiffer fabric bases allow a better acoustic outcomes and so does the copper conductive thread. Alas, the resources are limited, and hence for this scope, going forward with the silver coated conductive thread, stiff plain weave coated fabric, which surprising is giving out sharper and louder volume. Is it because of the coating?

Materials for rest of the ghungroos
Not to add a lot of layers between the speaker and the magnet, I decided to go forward with the speaker fabric for the rest of the ghungroos.



I found these large failed pincushions from one of my previous explorations, which ended up being too soft for pincushions but are perfect in size and feel for the padding. The stuffing is foam (like I said, not much of a success as a pincushion). Usually cotton, layers of rags or foam works as padding.



As for the circuit, I had modularity on my mind, hence decided to sew the soft circuit on an additional level. The only fabric that was stiff enough to support these many components yet open enough to make sewing easy and neat was this cotton slub fabric.



8. Construction



As I said, modularity was on my mind, and since this circuit has a lot of electrical components, I do not want to solder them in and make them unusable for other circuits. So, after rummaging my jewelry boxes, I found these hooks that work well with the teensy pins to not be loose, and they always keep contact. These can be remp4ed and fixed easily (well, not that easily since the sizes are *teensy* and need a bit of dexterity).



As for the actual traces, the space seemed too small to use fabric traces, hence I unwittingly decided to stick with conductive yarn. Although conductive yarn, in my experience give more glitches due to fraying. What might be a better option?

As for the modularity of the components, it was difficult to have them stay fixed while in use, and remp4e easily when needed. I considered pockets, but that would keep the pins inaccessible. And jumping off from there, through the arena of webs and nets, I decided to try open weave pockets. Due to the chips and buttons on the components, the open weave pockets held the components in place, allowed access to the pins, and the components were easily remp4able!



Onto sewing the circuit...



Scale and space was something that I certainly underestimated. The compactness made it extremely difficult to sew on all the traces!



9. Testing the soft circuit

After some calibrations for the accelerometer, and miraculously no glitches (usually I have noticed the glitches occur with LEDs more), the prototype worked.

The final prototype with a delayed response from the speakers so that the performer can pause and participate in the conversation.



10. Final outcome and next steps

From more efficient speakers, a better-finished outcome, machine stitched traces, and better planned traces, there is certainly a lot of room for updates. Since it is addressing a performance, and dance steps, the further steps will be to calibrate ghungroos in both the feet. And use machine learning to understand and take a note of the dance steps.

I would also like to replace the magnets with a fabric based electromagnet. Based on this research ➚ a half successful attempt at that is made below:



Reflections

1. Achievements
I was glad to figure out the code for the audio, especially since it took hours. I was also surprised to see the soft prototype working well with minimum glitches. I was also happy to use fabrics available around me without buying them or sourcing them. Learning from Liza’s methods of implementation, I assigned milestones or levels to what seemed like an ambitious task, starting from getting the sound to work, getting it to work with mp4ement, and getting it to work with machine learning, and I feel small goals help carry the task forward more efficiently. A modular approach made it feel like the outcome was acceptable. I am not completely satisfied with the soft circuit traces, but the solderless component-pocket with hooks approach seems something in the direction of accessibility. But I’m afraid it might be a lucky coincidence, and solderless approach might not be a great idea always. I guess we will find out with time and future trials and errors.

2. Challenges and regrets
Finding the correct combination of materials was certainly a challenge, especially when last-minute tasks do not work well with material sourcing. The scale was also definitely a huge challenge, and I might need to figure our a better way to make the traces other than hand and machine sewing with the conductive yarn. I am still unhappy with the number of hard components that are needed for this circuit. Can I convert the electromagnet and mp4ement-tracking part into soft components?

Not starting early was one of my biggest regrets, especially not sourcing the electrical materials early on, such as the conductive yarns and appropriate microcontroller. Not working on the soft electromagnet early on was also something I regret. It would have been a great opportunity to experiment with.

Since figuring out the working of the interaction took a huge time, I wasn’t able to explore as much with materials as I would have liked, such as thinking about how the ghungroos are tied, with a cord, velcro or a buckle? Would have also liked to have more functional embellishment on the surface to mirror the original look of the ghungroos. I am also a keen advocate of having transparent design and showing your work, and would have preferred the circuit to be visible. And lastly, time-management has been a major issue which always disturbs the documentation, and certainly regret not having a more organized documentation and a more creative tutorial.