Resources needed:
Tissue box with single hole at the top or small cardboard box with hole cut at the top; rubber band that is big enough to stretch around the box and over the hole; 2 pencils/markers/or crayons.

Description of investigation:
Background information: (10 minutes)
We are surrounded by sounds every day. Sounds are caused by vibrations, or the rapid back-and-forth motion of an object. These vibrations are transferred to the air molecules right next to the object, which bump into the molecules next to them, and so on, until the vibration reaches our ear.

Sometimes, these vibrations are obvious because they are big enough to see. For example, when you pluck a rubber band, you can see it move back and forth (or if you turn up the bass on a stereo with a large subwoofer, you may be able to see the speaker move). However, for the majority of sounds we hear every day, these vibrations are too small to see. For example, when you knock on a door, even though you can hear a sound, you cannot see the door vibrate at all. Sometimes you can still feel these vibrations even though you cannot see them. For example, if you place the palm of your hand on a door while someone else knocks on it, you will feel the knock. You can also feel your vocal cords vibrate if you put your hand on your throat while you talk or by simply feeling the pulse (your heart beating like in the previous lesson).

During this lesson, you will first explore how sounds cause vibrations using vibrations that are easy to see (such as using rubber bands). Then explore other vibrations that are harder to see, like knocking or talking. Finally, you will make your own sound and explain what vibrates and what creates the sound.

Engage: (5 mins)
First think about the question “What is sound”? Make a few sounds using objects at home (e.g. clapping your hands, writing on a cardboard, flipping the pages of a book). Then think about a different question: “What causes sound?” Elicit that sounds are noises that we hear, sounds happen when we talk, or sounds happen when two things hit each other.

Explore (20 minutes)
1. This part needs to be done in pairs, one person should hold one end of the rubber band in each hand and stretch it out. The other person should gently pluck the rubber band with one finger. Try this a few times.
Ask: What do you hear when you pluck the rubber band?
Discussion tip: We hear a sound.
Ask: What do you see?
Discussion tip: We see the rubber band move back and forth.
Ask: What happens when the rubber band stops moving?
Discussion tip: The sound stops.

2. Explain that the fast back-and-forth motion of the rubber band is called a vibration. When you pluck the rubber band, you make it vibrate. The rubber band in turn pushes on the nearby air, making it vibrate. Even though you can’t see the air vibrating, your ear can hear it. The vibration causes the sound. Since the vibration causes the sound, when the vibration stops (the rubber band stops moving), the sound also stops.
3. To build the rubber band guitar shown in the picture, stretch the rubber band around the tissue box, so it goes across the opening at the top. Place one pencil/crayon/marker under the rubber band on each side of the hole.
4. Now each person can hold the box with one hand and pluck the rubber band with the other hand. Take turns doing this and observe what happens. For example, what happens if you use your finger to stop the rubber band from vibrating? How does the sound change if they pluck the rubber band harder?
5. Demonstrate knocking on something hard at home, like a table, door, or wall.
Ask: What did we hear?
Discussion tip: We heard a sound.
Ask: What did we see? Could we see the vibration this time?
Discussion tip: No, we could not see the desk vibrate.
Ask: Do you think that there is still a vibration, even if we can’t see it?
Discussion tip: One might not believe that there is still a vibration if you can’t see it.

Explanation: All sounds are caused by vibrations, even if we can’t see them. To demonstrate this:
a. One should put his/her hand flat on a desk.
b. Another person should knock on the desk.
c. Switch roles and try again.

Ask: What did you see, hear, and feel when your partner knocked on the desk?
Discussion tip: We heard a sound. Even though we couldn’t see the desk vibrate, we could feel it vibrate with our hand.

Reflection: (5 mins)
Most of the vibrations that create sounds are too small for us to see. The rubber band provides a good example of vibrations because the vibrations are very big, so we can see them easily.
Revisit the questions you asked at the beginning of the lesson.

Assessment:
To assess each others’ understanding of sound and vibration, ask each other to think of a sound they can make at home (other than plucking their rubber band or knocking on a desk, which they’ve already done). Examples could include talking, tapping two pencils together, scratching their clothing etc. Explain to the rest of the family what vibrates to create the sound, and how they know this. For example, can they see or feel the vibration?
Identify more sounds around your home and figure out what vibrates to cause the sound.

Research Work: What do sound and vibrations have to do with cars?