# Student Guide: Measuring Heart Rate with Your Own Stethoscope

(In order to access the PDF you need a free Science Buddies account. Please or create a free account.)

### Summary

What do you think happens to people's heart rates when they exercise? You will find out by measuring another person's heart rate using a stethoscope you create with a cardboard tube, a funnel, and tape.

### Useful Vocabulary

• Heart: An organ in the body that is a powerful pump. When the heart contracts, it pushes blood to deliver oxygen through the body.
• Heart rate: The number of times a person's heart beats in an amount of time. This is usually measured in beats per minute (bmp). People's heart rates change if they have been resting or exercising.
• Sound: Invisible waves that travel through air or an object. As the waves move, they also move, or vibrate, whatever they travel through, a little bit. When these waves reach your ear, you hear them because they vibrate your eardrum. What these waves travel through can change whether you hear a loud sound or a quiet sound. For example, sound that travels through a closed door becomes quieter than if it traveled through an open door.
• Circulatory system: The set of body parts, including the heart, lungs, veins, and arteries, that help move blood all around the body.

### Materials

To do this activity you will need:

• Plastic funnel (1)
• A cardboard tube from a paper-towel roll (1)
• A strip of duct tape or other strong tape (1)
• Stopwatch or clock that counts seconds (1)

### Directions

1. Put the narrow end of the funnel into the cardboard tube. Using the strip of tape, tape the funnel and cardboard tube together. Make sure that there are no gaps or spaces where you tape the cardboard tube and funnel together.
 Figure 1. Tape the funnel to the cardboard tube using the duct tape. Make sure that the tape completely seals the tube and funnel together. You do not want any gaps or spaces where the tube and funnel are taped together.
1. Practice listening to the heartbeat of another student using your stethoscope. Put the funnel on the left side of the chest of another student. Make sure the funnel is flat against his or her chest. Why do you want to make sure the funnel is flat? Put your ear against the hole at the end of the cardboard tube. Do you hear the heartbeat?
 Figure 2. To listen to another student's heartbeat, put the funnel flat on the left side of the chest of the other student. Put your ear at the hole on the end of the tube.
1. If it is noisy or if the other student is wearing thick clothing, it may be hard to hear the heartbeat.
2. After the other student has been resting in a chair, listen to the heartbeat and count how many times it beats in 15 seconds. Multiply this number by four. This is the resting heart rate of the other student in beats per minute (bpm).
3. How does his or her heart rate change after he or she has exercised? Ask the other student to exercise in place for one minute by doing jumping jacks or running in place. Be careful not to disrupt the other student groups.
4. Right after the other student has stopped exercising, listen to the heartbeat and count how many times it beats in 10 seconds. Multiply this number by six. Why do you think you do this for only 10 seconds? How did the heart rate change after exercise? Did it change how you expected it to, or was it different than you expected?
5. Why do you think a person's heart rate changes right after exercising? Why do you think the heart changes how it beats? Hint: Think about what the heart does.
6. If a person regularly exercised, how do you think this would change his or her heart rate? How do you think that a person's heart rate during rest and heart rate during exercise would be different? Hint: Think about how regular exercise may change the heart.