Diddley Bow

In unit 2 of Light, Sound, and Time we focused on sound, how fast it can travel, and what it can travel fastest through. We also looked at waves, and how frequency plays a big role in understanding a wave, and with that we looked at the Doppler effect. Then we looked at instruments and how they produce sound, and how they can change frequencies, and this is how we learned about harmonics. Leading me to this action project, we are building a diddley bow, a type of guitar that only has one string on a piece of wood that uses a tin can. The materials used are a piece of wood (to use as a base), a tin can (to amplify the sound), a battery (to use a nut) and nails to hold everything down. I am most proud of having all materials in a short amount of time, and being able to build my guitar in the best way I could.

NVA "Diddley Bow" (2016) GCE Lab School

NVA "Diddley Bow Drawing" (2016) GCE Lab School

My diddley bow creates sound when the string vibrates, moving molecules in the air. The tin can helps with amplifying the sound to make it more audible. You could also use a slide on your string to check out different frequencies it can make. The diddley bow demonstrates a lot of key science concepts we went over like sound waves, because this is something that can actually produce sound waves. For frequency, it is shown by the tightness of the string we used, and the material we chose to use. From frequency we can then look at the wavelength and amplitude of the waves, and what they will look like. If it has a high pitch then the wavelength is shorter but the amplitude is the same. If it has a lower amplitude, then the volume is quieter.

The Doppler effect is where sound’s frequency can change according to a certain observer, when the source of the sound is moving. If I were running while playing my guitar and one man was standing behind, meaning I am running away from him, he would be hearing a lower pitch, because the sound waves get stretched out. If I were running towards him playing it, it would have a higher pitch because I am keeping up with the sound waves, so the frequency is higher.

For the string, the length is 15 inches and the thickness is 0.045 inches. To find the volume I need to do pi times radius squared times the height. The height is 4.25 inches and the radius is 1.6875, and using the formula, the volume of the guitar’s body (the can) is 38.02 inches cubed.

NVA "Diddley Bow Harmonics" (2016) GCE Lab School 

The picture above shows the harmonics involved with my guitar. Hertz (Hz) is the frequency unit, and centimeters are talking about the wavelength for each harmonic. To find each new harmonic you multiply the original frequency by whichever harmonic you are trying to find. So for the third I multiplied 117.92 by 3. For wavelength you do the opposite, you divide, so I would do 296.03 divided by 3.

I would not do anything differently, because I feel like I built my guitar in a special way, and that it turned out very well. One minor thing would be dulling the screws, because they do poke out of the bottom, which could be dangerous. Something I would do is sand them down, or just put a piece of wood under it to connect, so that they are completely covered. Below is audio of me playing my diddley bow.