Homemade Tunes

In unit two of my junior STEAM class "Light, Sound, & Time," we spent the past couple of weeks learning about sound.  We learned the anatomy of the human ear and how it perceives sound. We learned about the speed of sound, reflection and refraction, soundwaves, frequency, and wavelength. We learned about the Doppler effect and musical instruments. For our action project at the end of the unit, we had to make a one-string guitar or Diddley Bow out of common materials. 

CH. "Diddley Bow." 2021.

The Diddley Bow creates sound through the one guitar string. This guitar string is pulled tight between two nails that are mounted on a piece of wood. At one end of the string, there is a dead battery wedged underneath the string to create tension. The other end of the string runs through a soup can, this also creates tension. The tension allows the string to vibrate. The soup can then amplifies those vibrations the same way a soundhole does on a guitar. This creates the sound that we actually hear when the Diddley Bow is played.

CH. "Diagram." Google Drawings, 2021.

To make this guitar, I used a piece of wood, a soup can, a guitar string, an old battery, and screws. I used a screw to put a hole in the tin can so that I could string the guitar string through it. I used a screw as a tuning peg and a battery as the bridge, and I used screws to keep the can and battery in place. The width of my guitar string is 0.012 inches. 

CH · Diddley Bow - twang

The side view creates a trapezoid with bases of 1.38 inches and 1.63 inches, and a perpendicular height of 10 inches. This means it has an area of 10 x (1.38 + 1.63)/2 = 15.05 square inches. To find the angles, I divided my trapezoid into a rectangle with a triangle on top, with sides of 10.003 (hypotenuse), 10, and .25 (which is the difference between the two parallel sides, or 1.63 - 1.38). Therefore, the top right angle has a tangent of 10/.25, so my angle is tan-1(10/.25), or 88.57 degrees. To find the other angle, I subtracted that from 180 to get 91.43 degrees (because all quadrilaterals have 360 total interior degrees, and the bottom corners are both right angles).

CH. "Angles of Trapezoid." Google Drawings, 2021.

For the bridge of my diddley bow, I used a soup can. The soup can has a radius of 1.5 inches and a height of 5 inches.  The volume of the soup can is π(r)^2 x height = π x (1.5)^2 x 5 = 35.34 cubic inches. 

The section of my guitar string that vibrates is 10.003 inches long. I used an online tuner program and found that my open note is C#4, with about a frequency of 280Hz, and a wavelength of 1.225 meters, or 122.5 centimeters.

CH. "Instrument Harmonics." Google Drawings, 2021.

This project helped me understand the math concepts for wavelength and frequency a bit better. This project also helped me visualize the difference between wavelength and frequency. I had fun and an interesting time making this project. 

MTU. "Tuning." Physics of Music-Notes, https://pages.mtu.edu/~suits/notefreqs.html.