Wednesday, February 27, 2013

Musical Instrument Project

Of all of the projects I've done with my physics class, this is the only one that has consistently come out great. There are often high levels of achievement and a comparatively low risk of incomplete or far below-average projects. Managing these types of projects often means being pulled several ways at once, and the squeaky wheels can sometimes get the grease - it's a difficult balancing act, so look out for that. One thing that has helped this (and my honors physics independent project) has been to spread out the work days. Instead of four consecutive days, breaking those up into pairs or singles separated by other work (especially review activities) can help any groups that don't have an idea or are otherwise behind and increase the overall quality of the projects.

The task here was to create a musical instrument which is in tune with the rest of the musical world (providing evidence of that), can play a short but recognizable tune, and describing the timbre and standing wave properties by graphs and diagrams. At the end, the groups present their instruments and their mini-posters.

During the course of the project, each instrument is revised a lot; some completely change and some need model tweaks - using the end correction, sometimes the tension/wavespeed relationship or Helmholtz resonators (none of which they knew about before this). It's a great chance to really experience that prototype/revision cycle.

Here are some of the projects, and links to the recordings:

  • Capped tube marimba - this is an instrument made of PVC tubes, played with a mallet on the caps. Video

  •  PVC pan flute: this is really more of a PVC bugle assembly, made from five pipes played by one player. This had a really interesting behavior in that it behaved both like it had open ends and one closed end. Video

  •  PVC trumpets - similar to the one above, but played with teamwork. Some evidence of that dual behavior is seen here as well. Video

  •  Uketair - it's always difficult to build a string instrument. This group did a good job of building a resonating box, using shaved golf tees for stable tuning pegs, and making a bridge from a bolt. The fishing line strings stretch too much after tensioning, which makes it really difficult to keep in tune, but the principle's there. Video

  • Tuning fork resonators: these were custom-cut tubes that amplified the sounds of tuning forks. Even at that, they weren't super-loud, so they recorded the sounds and arranged the song in Garage Band. Video

  • Leg Marimba - this one was going to be a Blue Man Group PVC and paddle instrument, but the paddles didn't work too well, so they revised to using their hands and then (in a stroke of genius) to their legs. Video

  •  PVC Clarinet - This one wasn't really a clarinet, since it used buzzing, but the first design involved a reed. I had a couple of groups use reeds successfully last year, but none stuck with it this year. This was the first instrument that I've had with a reasonable implementation of holes to change the pitch. The timbre gets crazy after several are uncovered, but it does a reasonably good job of producing an intelligible pitch.
  • Batterie De L'eau (water drums) - this one also went through several revisions. By the end, they used a small strip of paper across a plastic container filled partially with water. By using the end correction, the contained resonated to selectively amplify the desired frequencies from the noise of the paper strip. It's a noisy sound, but the pitch is clearly audible. Video

  •  Pan Flute - this one's a PVC pan flute proper. The end correction proved a little trickier in here (I think that the face near the end affects the dynamics a bit, reducing that effective length), but worked out well overall. Video

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