Due Thursday April 19 at noon.
A waveguide drum wtih resonant body.
- Create a physical model of a bongo or similar drum using waveguides such that:
- The head of the drum (i.e. the surface membrane) is modeled as a three-node system. Two of the nodes represent points near the rim (i.e. edge) of the drum head, where the membrane is taut, because of the proximity to the rim. The third node represents the middle of the drum head, where the membrane is less taut. Each node should be connected to each of the others using bi-directional waveguides, but the ones between the rim-nodes and the center-node should be different than the one between the two rim-nodes.
- The body of the drum should be viewed as a resonator, and thus should likewise have a waveguide associated with it. It’s soiurce of sound should be the center node of the drum membrane.
- The excitation source for the drumstick can be a triangular impulse as I presented in my lecture notes. It should be jnjected into the center node of the drum membrane.
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Note that including the body of the drum, we actually have a four-node waveguide system, shown diagrammatically in the file DrumDiagram.pptx under the Resources tab on the Classess server.
But that diagram is just approximate — you may wish to use parameters to control various aspects of each kind of bi-directional waveguide, and you may wish to insert filters at suitable places to improve the sound.
- For extra credit, consider trying one or more of the following. In each case, document the differences in sound.
- Try different excitation sources for the stick: a square pulse, sinusoidal pulse, a noise burst, et,
- Try injecting the stick excitation source at a rim node instead of the center node of the drum membrane.
- Try forming a weighted sum of the 3 drum membrane nodes, and use this to drive the waveguide for the drum body,