Resources needed:
For the stethoscope: plastic funnel; a cardboard tube from a paper towel roll; a strip of duct tape or other strong tape; scissors.
For the string telephone: 2 cups; 2 paper clips; a string; tape; scissors/pin.

Description of investigation:
Engage (10 minutes)
Ask: Today, we will learn about sound travelling through materials. We shall focus on our heart and see how it produces a sound and afterwards we shall build a string telephone. Do you know what function the heart has in our body?
Discussion tip: The function of the heart is to make blood flow throughout the body.
Ask: Have you ever felt your heart beating when nervous or anxious? Why can you feel your heart beating more when nervous or anxious? Have you ever heard your heart beating?
Discussion tip: Our hearts beat faster when we react to stress or a perceived threat. Our body prepares to fight or flee.
Ask: Why would the heart beat faster when we perceive a threat?
Discussion tip: Your body needs more energy when it is on alert than it needs when it is in a relaxed state. Your body needs the blood to flow faster to make extra energy, and the heart is the organ that makes blood flow. By beating faster, more blood can be delivered.
Ask: Did you know that our heart is producing a sound every time it beats? Do you know how you can measure your heart rate? Prompt the children through questions like “What instrument do doctors or nurses us to listen to the heart and measure how fast it beats?”
Discussion tip: Nurses and doctors use a stethoscope. This is an instrument to listen to the noises made inside the body. It has a small disc that is placed on the body to pick up sounds, and a long air-filled tube that guides these sounds to the listener’s ear.
Ask: In this lesson, we will build our own stethoscope. We will use it to listen to the heart. What does the heart do that could make a noise, and how could we use it to measure how fast the heart beats?
Discussion tip: The heart squeezes and relaxes to pump blood through the blood vessels. The beats you hear are the heart valves closing with every beat (squeeze) of the heart. The number of beats (squeezes) in a specific time interval is a measure of how fast the heart beats.

Explore (20 minutes)
Make sure to follow these steps:
To build the stethoscope, insert the narrow end of the funnel into the cardboard tube and tape the funnel and cardboard tube securely together using the duct tape. Cutting the tape in small pieces or making incisions can help tape the funnel neatly to the tube.
2. Practice listening to the heartbeat of a parent/ guardian or another sibling using the homemade stethoscope. The one listening should place the funnel flat on the chest of another student, on the left side roughly where the heart is, and place the hole at the end of the cardboard tube against their ear.
Note: If there are other noises in the room, it can be difficult to hear, so try to have the windows and doors closed. Also, thick clothing may make it difficult to hear the heartbeat (sound does travel through materials but the more layers there are the less one is able to hear the sound).
3. Once you have practiced listening to each other’s heartbeats, discuss what sounds they hear with the stethoscope.
Ask: What sounds do you hear with the stethoscope? Does it sound like a heartbeat? Can you hear a pattern?
Discussion tip: You hear a regular pattern created by the beating heart. Each double beat (two short beats rapidly following each other) counts as one heartbeat. This heartbeat sound video is a good example.

Now that we’ve heard the sound of our heart beating we can investigate how sound travels through other materials. Encourage children to observe, investigate and listen to how sound travels around them. For example, by placing their ear on a table and observe any difference to sound heard.

For the next activity we shall build a string telephone and see if sound can travel through a string.

Explore (15 minutes)
Make sure to follow these steps:
1. Make a hole in the center of the base of both cups, using a pin or scissors.
2. Tie one paperclip to one end of the string.
3. Pull the other end of the string through the hole in one of the paper cups.
The paperclip should be inside the paper cup.
4. Insert the free end of the string into the hole in the bottom of the second
paper cup. Insert it from the outside of the cup.
5. Pull enough string through the hole to enable you to tie the second
paperclip to the end of the string.
6. Pull the cups apart so that in each cup the paperclip rests flat on the floor of the cup and the string is tense.
7. Take one cup, and have another person take the second cup. Walk away from each other until the string is stretched you’re now ready to use your paper cup phone.
8. Move closer to one another and try to speak now (one at a time). Did you notice any difference? Why is that?

Discussion:
How did the stethoscope help us hear our beating heart?
Why did the sound of our voice travel through the string telephone when the string was tensed and did not travel when the string was slacked?
Can you come up with other examples of sound passing through different materials? (perhaps communication under water)

Additional Resources: How telephones work – https://electronics.howstuffworks.com/telephone.htm