Diddley Bow making

For the second STEAM course of my junior year, I'm taking a course called Light, Sound and Time. This class is giving me a chance to explore and learn how to see, hear and measure time. The second unit was focused on sound and going over questions like how does sound travel? How fast does it travel? How do we hear sound? How do we make sound? We then went over the idea of even being able to control sound. During this unit I learned that light can travel faster than sound, which proved me wrong. For the action project, the class was assigned to build our own diddley bow. This was fun and interesting because we only were able to use recyclable items. I'm not used to using tools, so it was a bit hard, but I also saw this as a chance to learn how to use them. I'm proud of how I stayed on task making sure all my work was done for this project. I hope you enjoy hearing what I made below!

Making a diddley bow was actually pretty fun. The materials I used include: wood, a tin can, an old guitar string, a battery and screws. To get the guitar string through the can, I had to poke a hole into it with a nail. The battery worked as a nut, which made a big difference when it came to the tightness. The screws worked to hold my can and battery down.

RD. Diddley Bow sketch. (2016)

My instrument creates sound when the strings vibrate. When a slide is used, the note is changed because of the shortening of the vibrations. The tin can works as a sound hole or resonator that brings out those sounds. Depending on how you play your guitar, you'll have a different amplitude. If it produces a high pitch, the wavelength is going to be shorter but the amplitude will be the same. If it has a lower amplitude, the volume will come out quiter. This obviously also demonstrates another science principal like sound waves because it’s creating some.


In this class we also went over the idea of the Doppler effect. The Doppler effect is the change in pitch of a sound if it's moving towards or away from the listener. When you move toward the object producing sound, the pitch is higher and when you move away the pitch comes out sounding lower. So once I play my guitar and someone moves away, it’ll sound lower, and when you move towards me, it’ll sound higher.

Below are my measurments of my diddley bow:
Length of string: 23 cm
Thickness of string:0.34mm

RD.Diddley Bow. (2016)

RD. Diddley Bow. (2016)

RD. Diddley Bow. (2016)

To find the volume of my guitar's body I used the equation, 3.14r^2xheight. The height came out to be 10 cm and radius 2.5, so my equation looked like this: 3.14x6.25x10=196.25cm^3

When it came to finding the frequency and wavelength of my first 4 harmonics, my calculations came out to this:

RD. Labled Harmonics. (2016)

RD. Wavelength and Frequency calculations. (2016)

If I were to build one again, I would use a bigger tin can and see what sound that gives me, but I hope you enjoy hearing my first diddley bow!