Final Video presentation for MECH400: Computer Aided Engineering (Spring 2015)
The “seung” (ซึง) is a traditional guitar from the north of Thailand. During performance it is often paired with the fiddle known as “sloh” (สะล้อ) – both are integral instruments to Lanna musical culture (the name of the north of Thailand before it became part of Siam, and later Thailand) and have been the focus of my recent work. I know how to play both instruments.
Check out the actual resonators in part II through this link!
During my time at the MIT Media Lab, I got to meet and have coffee with Amit Zoran, then a PhD student and now a professor at the Hebrew University of Jerusalem, on his vision of Hybrids – the junction of two realms from computational technology and classical hand-hewn skills. Amit’s vision and projects have strongly inspired and influenced my own work.
Amit is the inventor of the Chameleon Guitar – an electric guitar with onboard Digital Signal Processing (DSP) that allows the user to acoustically change the sound of the guitar by literally swapping out the wood used as the front panel. I was particularly excited over one of Amit’s older projects – the Re-acoustic guitar, a concept design that allows users to switch out individual resonating chambers for each string of the guitar. The top string could have a mahogany chamber whereas the bottom string could have a walnut chamber, talk about customization! More importantly, the modular design democratizes the ability to customize the guitar using new and old fabrication techniques. Users could 3D print their own custom chambers and add these to the Re-acoustic guitar on-the-fly.
However, the Re-acoustic guitar remained a concept design as it was acoustically impossible to tether the chambers the strings and ensure an efficient transfer of vibrations.
I set out to solve this problem in my final project for MECH 400: Computer Aided Engineering. The class was my final Mechanical Engineering elective for my BS in Applied Physics.
There were two solutions to the problem: an acoustically virgin approach (absolutely no electronics) or an electro-acoustic approach that leverages signal processing technology developed in my senior thesis in Applied Physics.
I went with the first route.
Here were the first sketches. Any kind of plucked instrument – be it a seung, guitar or ukulele – has a bridge that transfers vibrations from the string to the one wooden body. In the case of a Re-acoustic guitar, each string must send vibrations to a separate wooden body (six in the case of a guitar, four in the case of a seung).
The acoustics demanded the single bridge to be “separated” into, essentially, one bridge for every string. Now, the chambers also need to sit under each string – but space is tight. So the bridges were distributed linearly. The chambers were designed to fit together and “swerve” in under the bridges.
This presents two problems:
- Distributing the bridges in this manner tampers with the tuning of the instrument.
- The bridge is not centrally located on the resonating chamber
However, for a first prototype, I decided to go ahead and fabricate to see if the concept would even work in the first place. The final design looks something like this:
I ran some simulations in Solidworks to ensure the frame was strong enough to withstand the forces.
As well as some frequency mode analysis on each of the individual chambers.
Some of the individual chambers are made from a combination of wood and clear acrylic.
Solidworks verified the design was structurally sound and that the chambers had resonant frequencies with the fundamental at around 2000 Hz. Given the small size of these chambers, that sounds quite reasonable albeit maybe a bit on the high end. Frequency analysis in Solidworks can be finnicky in the way constraints are set up. However, it does give a sense of the visual progression of each mode.