How do vibrating objects create sound waves?
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.
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!
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.
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.