Surrogate Soundboards for Thai instruments

The Sloh is a northern Thai string instrument made from steel strings and a coconut resonator. It is very similar to the Erhu in construction, but opts for a hemispherical resonator as opposed to the Erhu‘s cylindrical shape. I noticed that adafruit sells bone conducting actuators with a rectangular contact with almost the exact same geometry as the bridge of the sloh. My senior thesis in Applied Physics, nicknamed “Surrogate Soundboards,” looks at how to introduce artificial vibrations into the body of a surrogate instrument in a way that mimics the mechanics of the source instrument.

This solves the problem of contact geometry encountered when dealing with the violin – I had to create an adaptor that sits on top of the original violin bridge. Even my second prototype features the original feet stuck onto two independent actuators. However, one can mount the bone conducting actuator directly onto the front panel of the sloh.

Surrogate Soundboard 2.0SONY DSC

It would be interesting to develop this idea into a sloh with multiple physical resonators or tunable resonators (inspired by Amit Zorans Chameleon Guitar). Signal processing could be introduced in the captured signal and tuned before it hits the coconut resonator, allowing multiple chambers or materials to be simulated. What would a Sloh with a resonator the size of a football sound like?

Alternatively, the coconut resonator could be replaced with another actuator. This is because the resonator only “encloses” a volume of air that oscillates at its helmholtz frequency. This system can be modeled by an oscillating spring attached to the front wooden panel. This way, multiple elements of the system could be tuned to produce a one of a kind hybrid sloh!


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