In the second unit of the course Light, Sound and Time, we studied the speed of sound, echoes, the Doppler effect, Mach, rates, decibels, parts of the ear and how we receive sound. We also learned about harmonics, infrasound, audible hearing, ultrasound, sonar, how fast sound travels through materials, and how a guitar’s frequencies change through the strings. For our action project, we made a Diddley Bow. A Diddley Bow is a one string instrument made of a piece of wood, four screws, a battery and a tin can. During this action project I had difficulty getting tension on the string because my original idea was making a long Diddley Bow, but since I couldn’t get the tension needed, I made it shorter to get the right sound. From this project I learned that screwing a screw on a thick piece of wood with a screwdriver is hard and that to make a good sound for an instrument you need to be accurate with string tension and the type of string. I am proud of my Diddley Bow because it was difficult to build and to sound how I wanted it to sound and at the end I got it how I wanted it.
KIS. Diddley Bow. 2016.
The way my Diddley Bow produces sound using one string is that when I play it, it vibrates through the tin can which amplifies the sound. When it is played with a slide on the string it changes sound as it moves. For example, when it moves down towards the tin can the sound becomes higher because the strings vibration gets shorter and when moving the opposite way it sounds deeper and the string vibration gets longer. Depending on the thickness of the string it will most likely decide what type of sound will come out. For example on a thin string, the sound will be high pitch like a violin and on a thick string the sound will be low like a bass guitar. My instrument demonstrates pitch/frequency by the type of string. I chose a thick, short, tight wire string. Another thing that really helps with the sound is the size of the tin can because it changes how loud and clear your sound is. My Diddley Bow demonstrates sound waves because when I play the string, depending on how soft or loud I pluck the string it will determine the amplitude of the sound wave.
KIS. Sketch of Diddley Bow. 2016.
The Doppler Effect is when a frequency changes as it moves towards or away from the observer. The frequency get higher when it gets closer to the observer and the wavelength get shorter. The wavelength get longer and the frequency get lower when it moves away from the observer. My Diddley Bow can demonstrate this if I walk and play my instrument as I move towards someone who is standing still. As I move closer to the person the frequency is higher and as I move away from the person the frequency is lower.
The length of the string from the tin hole to the screw is 13 ½ inches, the diameter of the tincan is 4 inches and the radius is 2 inches. The height of the tin can is 5 ½ inches, the thickness of the string is 0.046 inches and the volume of the body is 69.11 inches. The way I got that is by using the equation “pi x r^2 x height.” The note of my string is F2, the frequency of that note is 87.31Hz and the wavelength is 395.16cm. The way I got the frequency and wavelength for my harmonics is by multiplying the 1st harmonic by 2 and dividing the wavelength by 2 and as I go on I just multiply and divide by the next number. The 1st harmonic is 87.31Hz (F) & 395.16cm (W), the 2nd harmonic is 174.62Hz (F) & 197.58cm (W), the 3rd harmonic is 261.93Hz (F) & 131.72cm (W) , and the 4th harmonic is 349.24Hz (F) & 98.79cm (W).
If I could do this project again I would choose a different string, maybe a thinner one because it was very difficult to get the right tension for a thick string so it might be easier for a thinner string. Also the pitch of my Diddley Bow would be much higher than it is and I would like that. Also I would use nails instead of screws because the nails would be more easier to get through the wood and I would have finished my project sooner.
KIS. Diddley Bow. 2016.
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