In this project, the Living Architecture Systems Group has partnered with a team of fourth-year mechatronics engineers from the University of Waterloo to produce an acoustic actuating device that is compatible with LASG testbed installations. The device is modelled after the clicking tymbal structure of a cicada. A tymbal is the flexible membrane on the cicada’s body, made up of bistable ribs that “click” from one side to another. Just as a cicada oscillates the ribs to produce its characteristic buzz, this device actuates a bistable metal rib to produce a clicking sound. In a production environment, several acoustic actuators would be arrayed across a sculpture to create a soundscape of clicks reminiscent of a warm summer’s night.
February 8, 2020
The first Cicada prototype was finished last week. After some tinkering, we were able to get the solenoids to actuate the rib in both directions. We tested multiple frequencies and resonating chambers, and took a number of videos to catalogue the sound we got out of each one.
Our first resonating chamber was a cookie tin, which was very loud but also quite tinny and unpleasant.
We also tried a plastic bowl, a glass bowl, and a ceramic pot. In our opinion, the plastic was the best option as it muted the tinnier frequencies and is lightweight.
Finally, we tried the device by itself, with no resonating chamber. It is much quieter in this configuration.
With the solenoids and rib now working, we’ve identified a number of avenues for improvement.
Firstly, even without the tin resonating chamber, the sound produced is quite metallic and mechanical. We believe that this is a result of the metal-on-metal impact of the solenoid on the metal rib. In the short term, we’re going to try applying a drop of hot glue to the tip of the solenoid to dampen the impact. We’ll also try replacing the metal rib with acrylic, and possibly wood veneer. However, it seems that the solenoids themselves make a clicking sound when they actuate, so we’re thinking of ways to dampen that as well.
Secondly, we may be able to replace the dual solenoids with a single solenoid powered by an H-bridge circuit, such as this one. The end of the solenoid would be attached to a C-shaped part that could push or pull the rib. This would lower the cost, weight, and size of our device. We’re ordering more MOSFETs and diodes in order to test this circuit out.
Lastly, we’d like to try shrinking the device. As you can see from the videos, it fits comfortably in two hands, but it’s possible that we can make it even smaller, especially if there’s only one solenoid.
Image credit: Gordon Winch, 2020
- Gordon Winch
- Jean Quirino
- Farhan Monower
- Jack Macdonald