This is the second action project for our STEAM course, Light, Sound, And Time. As the title of the course suggests, we are in the second unit called sound. In this unit, we were focusing on the basics of sound and how they correlate with instruments and other objects that produce sound. In our internal investigation of sound, we took a look at how instruments, specifically stringed instruments, produce sound. Afterward, we decided to make our own stringed instrument that could produce its own sound. This Action project is a lab report of what we came up with. Enjoy!
As we all know, stringed instruments, like guitars, violins, and harps, all produce sound. The interesting thing about these stringed instruments is that they can produce sound with different pitches. These pitches can vary depending on how long the string is or which section is being pressed. The same goes for the diddley bow that we made for this project.
JH, diddley Bow, 2021
Above, is a picture of my diddley bow, the stringed instrument we constructed. As you can see, It's a pretty simple build but the results are extraordinary. The instrument features an empty tin can, fishing wire, a long wooden plank, a battery, and a couple of screws. The can acts as the soundhole that disperses the sound waves emitted by the string when strung. The screws hold everything tightly in place. the sting of course is the main component of the instrument that allows it to be played. And last but not least, the battery holds the string at a certain tension which makes the sound nice and uniform.
JH, Instrument Diagram, 2021
And now, a recording of my diddley bow:
My didley bow produces sound just like any other stringed instrument; with vibrations. The string or wire that is strung on the instrument vibrates at a certain frequency that is above the human threshold of hearing. That frequency is then dispersed by the broad opening of the can or hole. As I said before, the pitch of the wave can be changed with the positioning of the battery or the amount of tension put on the string or wire. On any stringed instrument, there are 4 harmonics. On my didley bow, these harmonics have specific frequencies and wavelengths that affect the sound wave emitted out of the can. The first harmonic has an open note frequency of 264 Hz and a wavelength of 1.3 m. the second harmonic has a frequency of 528 Hz and a wavelength of .65 m. the third harmonic had a frequency of 792 Hz and a wavelength of .43 m. The last harmonic had a frequency of 1056 Hz and a wavelength of .32 m.
The measurements of my didley bow had some other interesting measurements as well. The base of my instrument was 23 inches long and the height was 1 inch which made the upper angle of my instrument was 87.51 degrees and the lower angle was 92.49 degrees. the volume was 59.06 and the area was 46. Lastly, the vibrating string itself was about 17 inches long and about .017 inches in diameter because I used 20 gauge fishing wire.
This project was pretty difficult but interesting at the same time. We got to learn a lot about sound and stringed instruments while getting to make our own as well. While the process for making the diddley bow was fairly easy, the measurements and calculations were the hardest part, because we were measuring a parallelogram when we were really measuring a triangle at the same time. That as well as measuring the harmonics and the frequency that the string was vibrating at, was pretty challenging. I would definitely recommend that any families or classes make a diddley bow because it was a fun and educational activity that helped a lot with getting a better understanding of sound.
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