Key Concepts
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Physics -
Sound wave -
Frequency -
Pitch
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Introduction
Did you know the modern guitars is an instrument that dates back more than 4,000 years? The first written guitar music was published in the 16th century, during a time when guitars still had strings made from animal intestines! Although guitars have a long history, they are still extremely popular in modern day music. Have you ever wondered how they make the music you listen to everyday? In this activity we’ll make our own guitars and test the different sounds we can create.
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Background
Sounds travel to our ears as sound waves – vibrations in the air we perceive as sound. These waves are generated by the vibration or movement of an object in a medium. They most commonly reach us by traveling via the air, although they can pass through liquids and solids – that’s why you can hear things underwater or if you press your ear up against a wall. A vibrating object, such as a tuning fork, generates a sound wave. The fork’s vibrations cause the air particles around it to vibrate at the same frequency. These air particles bump into the air particles around them, and the sound wave propagates outward from the tuning fork.
When a guitarist plucks a guitar string it vibrates at a specific frequency, which determines the pitch of the sound we hear. Faster vibrations produce higher-pitched sounds. Children generally have smaller, thinner vocal cords that vibrate much faster than those of adults. As a result, children’s voices sound much higher.
In this activity you will build your own guitar and explore how frequency changes the pitch of the sound we hear. Time to tune up!
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- An adult helper
- Four rubber bands of varying thickness but the same length
- Glue
- Packing take (or other strong tape)
- Empty tissue box
- Scissors
- Two large craft sticks
- Empty paper towel tube
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Preparation
- Remove the plastic inside the hole of the tissue box.
- Use the take to attach the paper towel tube to the short end of the tissue box. Make sure it is lined up with the box’s hole.
- Glue a craft stick to each end of the hole in the tissue box. The sticks should be perpendicular to the direction of the hole and close to its edges. Allow the glue to dry.
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Procedure
- Wrap each rubber band round the tissue box lengthwise so they rest on the craft sticks. The rubber bands can cross over the hole in the tissue box top, but they don’t need to as long as they’re resting on the craft sticks.
- Hold your guitar by the paper towel roll, and gently pluck each rubber band. Do all of the rubber bands sound the same? If not, which makes a higher-pitch sound, the think or thick rubber bands? In addition to sound, can you feel anything happening when you pluck the rubber bands?
- Choose one rubber band and pluck it. Listen carefully to the sound it makes. Press your finger down on the rubber band so that it is pinched between your finger and one of the craft sticks. Does the sound change when your finger is pressed on the rubber band? If so, what changes about it?
- Try pressing each rubber band down on the craft stick. Notice how this changes the sound the rubber band makes.
- Extra: Try increasing the size of the tissue box hole. How does this change the sound?
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Observation and Result
The sound made by your instrument was the sound created by the rubber band vibrating when you plucked it, much like how a real guitar string vibrates when played by a musician. As you strummed the strings of your instrument you might have noticed you could feel the vibrations of the rubber band traveling through the tissue box.
The thickness of the rubber band changed the tone of the sound you herd when you plucked it. The thinner strings on a guitar make a higher-pitch sound because they can vibrate more quickly than the thicker ones. The thinner strings on your rubber band guitar are the same – they vibrate more quickly, and we perceive these vibrations as a higher-pitched sound.
When you held the rubber band down the sound changed and eventually there was no sound at all. From this you could observe the sound was created by the rubber band- and when you prevented the rubber band from moving you couldn’t produce any sound.
In addition, in this activity you should have noticed you could change the pitch of the sound by pressing down on the rubber band. When you pressed down on it, the vibration section of the rubber band got shorter. As a result, the pitch of the sound got higher.
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Safety First & Adult Supervision
- Follow the experiment’s instructions carefully.
- A responsible adult should assist with each experiment.
- While science experiments at home are exciting ways to learn about science hands-on, please note that some may require participants to take extra safety precautions and/or make a mess.
- Adults should handle or assist with potentially harmful materials or sharp objects.
- Adult should review each experiment and determine what the appropriate age is for the student’s participation in each activity before conducting any experiment.
Next Generation Science Standard (NGSS) Supported - Disciplinary Core Ideas
This experiment was selected for Science at Home because it teaches NGSS Disciplinary Core Ideas, which have broad importance within or across multiple science or engineering disciplines.
Learn more about how this experiment is based in NGSS Disciplinary Core Ideas.
Physical Science (PS) 3: Energy
Grades 3-5
- 4-PS3-2,3. Energy can be moved from place to place by moving objects or through sound, light, or electric currents.
Grades 3-5
- 4-PS3-2. Energy is present whenever there are moving objects, sound, light, or heat. Light transfers energy from place to place. Electric currents also transfer energy from place to place to produce motion, sound, heat, or light.
- 4-PS3-3. When objects collide, energy can be transferred from one object to another thereby changing their motion. In such collisions, some energy is typically also transferred to the surrounding air; as a result, the air gets heated and sound is produced.
Physical Science (PS) 4: Waves and Their Application in Technologies for Information Transfer
Grades K-2
- 1-PS4-1. Sound can make matter vibrate, and vibrating matter can make sound.
Grades 3-5
- 4-PS4-1. Waves of the same type can differ in amplitude (height of the wave) and wavelength (spacing between wave peaks).
Grades 6-8
- MS-PS4-1. A simple wave has a repeating pattern with a specific wavelength, frequency, and amplitude.
- MS-PS4-2. A sound wave needs a medium through which it is transmitted.
Grades 9-12
- HS-PS4-1. The wavelength and frequency of a wave are related to one another by the speed of travel of the wave, which depends on the type of wave and the medium through which it is passing.
- HS-PS4-3. Waves can add or cancel one another as they cross, depending on their relative phase (i.e., relative position of peaks and troughs of the waves), but they emerge unaffected by each other.
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