This past Unit, our class has been studying sound. We are all familiar with what sound is and how important sound is in our everyday lives, but do we really understand the science behind sound? We visited CHS to speak with people who are deaf, about what technologies they use to communicate with people who cannot sign and help others who are also deaf. We learned how frequencies are measured and how they are heard through our ears. Taking everything that we learned over the unit, we made a diddly bow. A diddly bow is basically a one-stringed guitar, but if you want to learn more about it, continue reading.
This is an image of the diddly bow I created. I took a 0.508 mm thick guitar string and wrapped it around a screw. Then I screwed it into the wood plank on one end, which is the side with the red line. Then I pulled the other end of the string through the hole that I poked in a tin can. I pulled the string across the wood piece as tight as I could and screwed it into the wood after wrapping it around a screw. Then I used another screw to keep the can in place. Normally a battery is placed just under the string by the redline to act like a nut and add more tension, but because my string had enough tension, I did not add a battery.
The marked lines in the images are the harmonic frequencies of the string. It is measured from the redline to the bottom of the tin can. A harmonic frequency is a repeating signal, that is also a standing wave. The first harmonic includes two nodes, and the second harmonic will include a third node. The number of nodes will continue to increase as we go further up the harmonic scale. This is an image of the first and second harmonic for reference.
This is a sketch I have created with labeled measurements of the right triangle on my diddley bow. The upper and lower angles are also labeled. You can check my calculations at the end of this blog post.
When you pluck the string on the didley bow, the vibrations travel throughout the string, and to the bridge and resonate in the hollow body of the diddley bow. The vibrations then escape through the soundhole, which is the opening of the can. Continue reading to learn how these vibrations travel through your ear as you listen to the audio recording of my diddley bow.
Here is a closer visual of the resonator/soundhole on my didley bow, which includes its measurements as well. The volume of the tin-can is 30.93 in.^2You can check my calculations at the end of the blog post.
This is an audio recording of the didley bow. In the recording, I tried to follow the do-re-mi scale. It is not very accurate but was worth the attempt. As you are listening to this audio, try moving at a very fast rate away from the speaker of your computer. If you are listening from a phone, try moving the phone speakers back and forth from your ear very fast. If you are hearing a change in pitch or speed, this means that the doppler effect is taking effect.
For those that do not know, the doppler effect is the increase or decrease in the pitch of the due to the source, or observer moves farther or closer to one another. When you move closer to the source of a sound, it sounds higher-pitched, and when you move away from it, it sounds lower-pitched. This applies to when the source moves toward you, the observer.
When you play the audio recording, keep in mind that the vibrations will travel to the pinna in your ear. That is the tube that connects the outside of your ear to the oscillates. The ossicles are the three bones in your ear that transmit vibrations to the eardrum. The names of the bones are the hammer, anvil, and stirrup. After the vibrations travel through the ossicles, they enter the eardrum and cause it to vibrate. This sends the signals throughout the inner part of your ear, which is called the cochlea. In response to the vibrations it receives from the eardrum, it creates nerve impulses to the brain.
Making a didley bow was really engaging because we were not only creating an instrument that we hear almost everywhere in the world, but we were also learning how the strings on guitar work. I learned how the general scale of the strings on a guitar is, and how to recreate it on a didley bow. I really enjoyed creating this diddley bow, and would highly recommend this to anyone who is interested in music and the science behind wavelengths.
CALCULATIONS
Upper Angle : 87.3 degrees
Tangent = Opposite/Adjacent >>
T = 26/1.5 >>
T =17.33... >>
17.33... x Tan^-1 = 86.69... >>
87.3 degrees
- - - - - - - - - - - - - - - - - - - - - - - -
Lower Angle : 3.3 Degrees
Tangent = Opposite/Adjacent >>
T = 1.5/26 >>
T = 0.057... >>
0.057... x Tan^-1 =3.301... >>
3.3 Degrees
- - - - - - - - - - - - - - - - - - - - - - - -
Volume of Tin-can : 30.93 in.^2
Area of a circle = Pi x R^2 >>
Area = Pi x 1.5^2 >>
Area = Pi x 2.25 >>
Area = 7.07
Volume = Area x Height >>
Volume = 7.07 x 4.375 >>
Volume = 30.93 in.^2
This is an image of the diddly bow I created. I took a 0.508 mm thick guitar string and wrapped it around a screw. Then I screwed it into the wood plank on one end, which is the side with the red line. Then I pulled the other end of the string through the hole that I poked in a tin can. I pulled the string across the wood piece as tight as I could and screwed it into the wood after wrapping it around a screw. Then I used another screw to keep the can in place. Normally a battery is placed just under the string by the redline to act like a nut and add more tension, but because my string had enough tension, I did not add a battery.
 |
| ALL (2020) Visual of entire diddley bow with marked harmonic frequencies |
FIRST HARMONIC THIRD HARMONIC
Frequency : 101.2 Frequency : 303.6
Period : 1/101.2 Period : 1/303.6
Wavelength : 26 in. Wavelength : 8.67 in.
SECOND HARMONIC FOUR HARMONIC
Frequency : 202.4 Frequency : 404.8
Period : 1/202.4 Period : 1/404.8
Wavelength : 13 in. Wavelength : 6.5 in.
The marked lines in the images are the harmonic frequencies of the string. It is measured from the redline to the bottom of the tin can. A harmonic frequency is a repeating signal, that is also a standing wave. The first harmonic includes two nodes, and the second harmonic will include a third node. The number of nodes will continue to increase as we go further up the harmonic scale. This is an image of the first and second harmonic for reference.
When you pluck the string on the didley bow, the vibrations travel throughout the string, and to the bridge and resonate in the hollow body of the diddley bow. The vibrations then escape through the soundhole, which is the opening of the can. Continue reading to learn how these vibrations travel through your ear as you listen to the audio recording of my diddley bow.
 |
| ALL (2020) Labeled measurements of tin-can |
Here is a closer visual of the resonator/soundhole on my didley bow, which includes its measurements as well. The volume of the tin-can is 30.93 in.^2You can check my calculations at the end of the blog post.
This is an audio recording of the didley bow. In the recording, I tried to follow the do-re-mi scale. It is not very accurate but was worth the attempt. As you are listening to this audio, try moving at a very fast rate away from the speaker of your computer. If you are listening from a phone, try moving the phone speakers back and forth from your ear very fast. If you are hearing a change in pitch or speed, this means that the doppler effect is taking effect.
For those that do not know, the doppler effect is the increase or decrease in the pitch of the due to the source, or observer moves farther or closer to one another. When you move closer to the source of a sound, it sounds higher-pitched, and when you move away from it, it sounds lower-pitched. This applies to when the source moves toward you, the observer.
When you play the audio recording, keep in mind that the vibrations will travel to the pinna in your ear. That is the tube that connects the outside of your ear to the oscillates. The ossicles are the three bones in your ear that transmit vibrations to the eardrum. The names of the bones are the hammer, anvil, and stirrup. After the vibrations travel through the ossicles, they enter the eardrum and cause it to vibrate. This sends the signals throughout the inner part of your ear, which is called the cochlea. In response to the vibrations it receives from the eardrum, it creates nerve impulses to the brain.
Making a didley bow was really engaging because we were not only creating an instrument that we hear almost everywhere in the world, but we were also learning how the strings on guitar work. I learned how the general scale of the strings on a guitar is, and how to recreate it on a didley bow. I really enjoyed creating this diddley bow, and would highly recommend this to anyone who is interested in music and the science behind wavelengths.
CALCULATIONS
Upper Angle : 87.3 degrees
Tangent = Opposite/Adjacent >>
T = 26/1.5 >>
T =17.33... >>
17.33... x Tan^-1 = 86.69... >>
87.3 degrees
- - - - - - - - - - - - - - - - - - - - - - - -
Lower Angle : 3.3 Degrees
Tangent = Opposite/Adjacent >>
T = 1.5/26 >>
T = 0.057... >>
0.057... x Tan^-1 =3.301... >>
3.3 Degrees
- - - - - - - - - - - - - - - - - - - - - - - -
Volume of Tin-can : 30.93 in.^2
Area of a circle = Pi x R^2 >>
Area = Pi x 1.5^2 >>
Area = Pi x 2.25 >>
Area = 7.07
Volume = Area x Height >>
Volume = 7.07 x 4.375 >>
Volume = 30.93 in.^2
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