Instructables

Musical Junk Physics Project

This project is not for me. It is for someone who inquired on Answers. Here was his original text:


It's a project for physics, and it sounds impossible. I also have to play it in front of the class and have a written component with an explanation on what resonance is occurring. No electric instruments.

Objectives:

1. Construct a musical instrument out of junk and common materials such as plastic pipe, wood, glass, metal scrap, etc.

2. Demonstrate and explain physics concepts inherent in your instrument.

Rules:
1. The instrument must be able to play an octave in tune to receive a B grade.

The A grade is reserved for truly amazing instruments in terms of thought and construction, so my challenge to you is to WOW me.

2. The instrument must be able to play a song. Songs such as "Mary had a Little Lamb" or "Twinkle Twinkle Little Star" are not adequate since they do not include all the notes in an octave.

3. No Kazoos, Jew's Harps, Pop bottles filled with water, musical saws, washtub basses etc. When in doubt, ask.

4. This is a high school level assignment, so I am expecting high school level (or above) projects at an appropriate level of difficulty.

5. Grading will be based on
  • # of notes played
  • ability to make your instrument resonate
  • appropriate difficulty of the instrument construction
  • your song of choice in an auditory presentation to the class and an explanation of the physics behind your instrument
  • creativity of course.

Stringed instruments must have more than one string


Let's help him out!!!

slash513 years ago
My daughter while in junior high, with my guidance, made a pan flute from bamboo growing in the neighborhood. Tuning was done by trimming the lengths.
A xylophone can be made from discarded pipes. I have demonstrated the resonating frequency using a 20 foot length of bungy cord. I would tie off one end and then get the rope oscillating. Then I would have two young volunteers grab points where the rope were still. After that demonstration I would hold a metal pipe and tap it while moving my hand closer to the "sweet point."
What about making a flute made of a scrap 3/4 inch diameter PVC?
I have the same project as that that i need to do
BeanGolem (author)  ME is the best4 years ago
 what are your initial thoughts?
They get 'em out of the same book (or just copy off each other...)

L
Goodhart5 years ago
2. The instrument must be able to play a song. Songs such as "Mary had a Little Lamb" or "Twinkle Twinkle Little Star" are not adequate since they do not include all the notes in an octave.

Well, that excludes the music from almost any Beatles song then too. ;-)
BeanGolem (author)  Goodhart5 years ago
The rule does not say, however, that the song must have been written prior to this assignment.
I know, I just meant that most songs have 3 chords in the music (if you take away the singing portion, and listen to only the music). There are very few pieces that use the entire 12 chords of the scale IIRC.
BeanGolem (author) 5 years ago
If you want an all-encompassing song, I would use "Joy to the World" because the first eight notes are a descending major scale. One octave. done.
BeanGolem (author) 5 years ago
Types of Instruments:

Musical instruments use a few different techniques to resonate.

String instruments amplify the vibration of the string with a resonator box, like the body of a guitar or violin. The physics behind this relates to the mass of the string and the tension in the string. Your physics text probably describes the equations somewhere. Low pitch strings are massier and looser than the high pitch strings. If you are going to make one of this type, you will need to have several string of different tension/mass and some sort of resonator box. This would probably be the easiest way to get a lot of different notes.

Brass instruments themselves are a resonator, amplifying the vibration you create with your lips. To resonate low pitches, you make the horn "longer" by adding tubing. This is most easily pictured on a trombone, where the slide can be seen moving in and out. The physics behind this is that your lips create pressure waves that resonate the air in the horn. When the horn's natural frequency (determined by length) and the pitch you are buzzing match, you achieve resonance. However, you can also achieve resonance on any of the higher modes above the natural frequency of that length. This is what makes a brass instrument "jump" between different pitches at any given horn length. Replicas of brass instruments are easy to make with tubing. The hard part is getting it to resonate on each pitch of a scale, which is unnatural to how the vibration modes work. You must be able to change the length of tubing to achieve resonance at each pitch on a scale.

Reed instruments vibrate one or two reeds and then the horn resonates that sound. These achieve resonance by making the horn the correct length to match the fundamental frequency of the reed vibration. The difference between these and brass, however, is that the horn almost always functions at a given lengths fundamental frequency and does not utilize the higher harmonics as much. By covering holes with your fingers, you lengthen the horn and get a lower pitch. A clarinet is one of the most common examples.

Flutes use the oscillation of air over a hole to create the vibrations that are resonated by the instrument. Jugs work this way, too. The vibration is actually the air switching between going inside the instrument and going outside the instrument. Again you would cover holes to lengthen the instrument and change the fundamental frequency.

Here is a fantastic resource about the basics of many types of instruments.

I'm biased towards brass instruments, as it is what I play. (That's a euphonium.)

As a first step, I would poke around the fantastic resource I mentioned above. Decided which type of instrument you want to tackle, and then we can discuss materials and options. I vote brass, but it may be a good challenge. That would just net you that "A" you want, though. And I would have much more to offer.

Jeez, now you got a ton of ideas floating zipping around my brain. Let's continue this in the forums.

Oh... you might have to join Instructables for that. But you should anyway, since you'll be posting an I'ble of your project ;)
gmoon BeanGolem5 years ago
I'd like to add the percussion class to your list, such as xylophones, chimes and bells...
BeanGolem (author)  gmoon5 years ago
haha. forgot percussion. I guess that's what happens when I write this stuff at 1:30am. Feel free to write a blurb on percussion! (percussion is way too easy to make imo. heh. although describing the physics of a drum head can lead to some pretty cool 3D math functions)
What about a steel drum ;-)
lemonie5 years ago
Use "Twinkle, twinkle little bat" instead, it's the same tune. For the physics, refer to standing waves / resonance / wavelength - as long as you understand what you're talking about you're there. L
Kiteman5 years ago
It is by no means impossible, and is a regular homework project set for the Year 5s at my school (aged 9-10).

Over the years, my favourite was an inside-out double base-type thing.

It was basically a ten-foot length of plastic drain pipe.

It had two bolts through it (one at each end) and lengths of fishing line tied to the bolts.

The lines were all at slightly different tensions, and it was played by reaching through a large hole cut in the side of the pipe and plucking the strings.

If you're after something slightly more portable, try this or this, or this.

A very special project would be this Hank Drum.
Kiteman Kiteman5 years ago
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