Rubber Band Bass Guitar
Pick up some good vibrations in this activity to try out with your family and discover the physics behind every bass-line.
See https://youtu.be/GJ-i1KJKqgk for the video.
Before you start:
These experiments have not been specifically safety tested for home use but we believe them to be safe if the instructions are followed. Adult supervision or direction is recommended as appropriate. All experiments are carried out at your own risk.
What you’ll need:
A rubber band. If you have different shapes and sizes, even better!
What to do:
In this activity you’ll be listening to sounds by putting your finger in your ear. Wash your hands before doing this and remember never to force your finger (or any other object) into your ear.
- Take your rubber band. Stretch it between the index finger and thumb of one hand.
- Gently put your index finger in your ear. Don’t push hard, but make sure there’s a seal, as if you were trying to block out a loud noise.
- Twang the band with the index finger of your other hand. You should hear loud sounds like a bass guitar.
- Change how much the band is stretched by moving your fingers closer together or farther apart. Stretching the band increases the tension in the band. Can you adjust the band so that you can play two different notes on the two halves of the band?
- Take your finger out of your ear, but keep twanging the band. How does the sound change?
- Once you’ve got the hang of it, see if you can play any famous basslines, like Seven Nation Army or Another One Bites the Dust.
Things you could ask:
- What makes the sound and how does it get into your ear?
- How does the sound change when you stretch the rubber band more or less?
What’s going on?
A sound is made when something vibrates. Take your rubber band, stretch it out and give it a twang. You can even see these vibrations! The vibrating band makes the air nearby vibrate, and the vibrations spread out in all directions. If your ear is nearby, you will hear the sound as the vibrations make your eardrum and the bones in your ear vibrate as well.
In our rubber band bass guitar, the vibrations travel through your finger to your ear. Sounds travel better through solids like your finger than through gases like the air. This is because the molecules in a solid are so much closer together than in a gas so it is easier for the vibrations to be passed along. As soon as you take your finger out of your ear, there is a gap of air so the sound gets quieter.
You can change the pitch to create your basslines as you stretch and release the band. The more you stretch the band, the more tension it is under and the faster it vibrates up and down. The number of vibrations every second is called the frequency and this tells you exactly how high or low the note is. A guitarist does the same thing when tuning their guitar by turning the fiddly things on the neck of the guitar to stretch or relax the string.
What next?
Investigate together and discover how the sound changes when you use:
- A thicker or thinner band
- A longer or shorter band (You can shorten a long band by tying a knot in it)
- Knowing what you do about vibrations, can you predict what will happen?
Did you know?
The study of sound itself is called acoustics. This is also the name for non-electronic music – so your rubber band bass experiment is both!
Thank you to the Institute of Physics for permission to use this idea