Abstract

Objective

Introduction

Ever wonder how the doctor can hear your heart beating? You've probably seen that the doctor uses a tool called a stethoscope to do this. A stethoscope is a long, thin plastic tube that has a small, flat disc or hollow cup on one end and earpieces on the other end. The doctor puts the flat disc or hollow cup on the patient's body, and the earpieces go into the doctor's ears. Look at Figure 1 below to see a photograph of a stethoscope.

Figure 1. A doctor uses a stethoscope, like the one shown above, to hear small sounds inside a patient's body, such as the sound of the heart beating.

Using a stethoscope, the doctor can hear sounds inside a patient's body. How does it work? The disc and the tube of the stethoscope amplify small sounds, or make sounds louder. This amplified sound travels up the stethoscope's tube to the ears of the doctor, who hears the sound through the earpieces.

A doctor can use a stethoscope to listen to a patient's heart, lungs, and other small sounds within the body. Every time a heart beats, it pushes blood through the body, and the beating noise can easily be heard using a good stethoscope. Very good stethoscopes can let the doctor hear even quieter sounds in a patient's body.

What parts of a stethoscope are most important for making it work well? Why would some stethoscopes amplify sound better than others? In this science fair project, you will make three different homemade stethoscopes and investigate why one stethoscope design works better than other designs.

Terms, Concepts, and Questions to Start Background Research

• Stethoscope
• Amplify
• Heart beats

Questions

• How does a stethoscope work?
• What do doctors use stethoscopes for?
• Why do you think one stethoscope would work better than another?

Bibliography

Have an adult help you do further research by visiting the following websites, which give information about stethoscopes:

• WakeMed Voices. (2011, September 7). Did you ever wonder how a stethoscope works? Retrieved September 20, 2011, from http://wakemedvoices.org/2011/09/did-you-ever-wonder-how-a-stethoscope-works/
• Schunk, K. (n.d.). What is a stethoscope and how does a stethoscope work? Acoustic Heart. Retrieved September 20, 2011, from http://acousticheart.com/what_is_a_stethoscope_and_how_does_a_stethoscope_work.html
• 3M^TM Littmann® Stethoscopes. (n.d.). History: The evolution of an essential tool. Retrieved September 20, 2011, from http://solutions.3m.com/wps/portal/3M/en_US/3M-Littmann/stethoscope/littmann-learning-institute/about-stethoscopes/stethoscope-history/
• KidsHealth. (n.d.). Stethoscope. Retrieved September 22, 2011, from http://kidshealth.org/kid/word/s/word_stethoscope.html

For help creating graphs, try this website:

• National Center for Education Statistics. (n.d.). Create a Graph. Retrieved June 2, 2009, from http://nces.ed.gov/nceskids/CreateAGraph/default.aspx

Materials and Equipment

• Large plastic funnels (3)
• Small plastic funnels (2)
• Plastic tubing, at least 15 inches long
• Ruler or measuring tape
• A pen that can write on plastic
• A pair of strong scissors or utility knife
• Small garden hose, at least 15 inches long
• Electrical tape
• Duct tape
• A cardboard tube from a paper-towel roll
• Lab notebook
• Graph paper

Shop for Supplies at Science Buddies Online Store

Science Buddies has compiled some suggestions for harder to find items in our Amazon store. The store does not include every item for every project, but it does include items that we feel work for the projects on our website. If you have comments or would like us to add items to the store, please contact us at scibuddy@sciencebuddies.org.

Experimental Procedure

Making Three Different Stethoscopes

In this part of the science project, you will make three different homemade stethoscopes.

1. Make the first stethoscope with a large funnel, a small funnel, and the plastic tubing. You can see a picture of this stethoscope in Figure 2 below.
   1. Measure 15 inches of plastic tubing. When you measure, make sure to lay the tubing flat against the ruler or measuring tape. Mark this point on the tubing with a pen.
   2. Have an adult help you cut the plastic tubing where you marked it with the pen. The cut tubing should be 15 inches long.
   3. Put a small funnel in one end of the tubing, and a large funnel in the other end.
      1. If it is hard to put the funnels in the tubing, soak the tubing in warm water to soften the plastic and try again. If this doesn't work, tape the tubing to the funnels. Make sure that the tape is holding the funnel and tubing together tightly.

Figure 2. The first homemade stethoscope design connects two funnels, one large and one small, together using plastic tubing.

2. Make the second stethoscope with a large funnel, a small funnel, the small garden hose, and electrical tape. You can see a picture of this stethoscope in Figure 3 below.
   1. Measure 15 inches of garden hose. When you measure, make sure to lay the hose flat against the ruler or measuring tape. Mark this point on the hose with a pen.
   2. Have an adult help you cut the hose where you marked it. The cut hose should be 15 inches long.
   3. Put a small funnel in one end of the hose and a large funnel in the other end.
   4. Tape the funnel and hose together with electrical tape.

Figure 3. The second homemade stethoscope design connects two funnels, one large and one small, together using a piece of garden hose. Electrical tape is used to securely attach the funnels to the hose.

3. Make the third stethoscope with a large funnel, the cardboard tube, and duct tape. You can see a picture of this stethoscope in Figure 4 below.
   1. Insert the narrow end of a large funnel into the cardboard tube.
   2. Tape the funnel and cardboard together using duct tape.

Figure 4. The third homemade stethoscope design connects one large funnel to a cardboard tube using duct tape.

Testing Your Stethoscopes

1. Listen to the heartbeat of a helper using each one of your homemade stethoscopes. If there are other noises in the room, it can be difficult to hear using the stethoscope, so make sure you are in a quiet place. Also, thick clothing may make it difficult to hear the heartbeat.
   1. Place the large funnel of the stethoscope on your helper's chest, over where his or her heart is.
   2. Put the small funnel against your ear, covering it. For the third funnel, put the hole at the end of the cardboard tube against your ear.
   3. Listen for your helper's heartbeat.
2. Which stethoscope made it easiest for you to hear your helper's heartbeat? Which stethoscope was the hardest to hear your helper's heartbeat with? Make a table in your lab notebook like the one below. Write down in your table how loud the heartbeat sounds were for each stethoscope. Write down that the heartbeat sounds were "soft," "medium," or "loud."

3. Score how loud each heartbeat sound was with a number. For example, "soft"= 1, "medium"= 2, and "loud"= 3. Using these numbers, make a bar graph of how loud the heartbeat sounds were using each stethoscope.
   1. You can make a graph by hand or use a website like Create a Graph to make a graph on the computer and print it.
   2. Put each stethoscope's number on the x-axis (the horizontal axis going across) and how loud the heartbeats were on each stethoscope on the y-axis (the vertical axis going up and down).
      1. For example, a "soft" heartbeat will be low on the y-axis, whereas a "loud" heartbeat will be high on the y-axis.
4. Why do you think one of the stethoscope designs worked better than another design? What part of the better design do you think made it work better?
   1. Do you think it was the tubing, the funnels, or some other part that made one stethoscope work better than another?

Variations

• You probably just found that some stethoscope designs work better than others. But why is this? What goes into making a good stethoscope design? To investigate how you can improve on a stethoscope design, visit The Engineering Design Process page.
• Make one of the stethoscopes again but find something to change. For example, use longer or shorter tubing, or tubing of a different material or size, or a different size funnel. How does this change how well the stethoscope works? Did it make it better or worse?
• Use your best homemade stethoscope and measure your helper's heart rate. The heart rate is the number of times the heart beats in one minute. Take your helper's pulse and compare this to the heart rate you got using your stethoscope. To learn about heart rates and taking someone's pulse, see the Science Buddies' Project Idea A Day in the Life of Your Heart.
• If you've seen and felt a real doctor's stethoscope before, think about how the best homemade design you tested is different from a real stethoscope. What parts are different, and how are they different? How do you think the differences make the real stethoscope work better or make it easier to use all of the time?

• For more science project ideas in this area of science, see Human Biology & Health Project Ideas.

Credits

Teisha Rowland, PhD, Science Buddies

The designs for the stethoscopes were based on materials from:

• CSIRO. (n.d.). Try this: Make your own stethoscope. Retrieved September 20, 2011, from http://www.csiro.au/helix/sciencemail/activities/Stethoscope.html
• Science With Me! (2011, January 12). How to make a Homemade Stethoscope. Retrieved September 20, 2011, from http://www.sciencewithme.com/how-to-make-a-homemade-stethoscope/
• Bodine, Alicia. (n.d.). How to Make a Homemade Stethoscope. eHow. Retrieved September 20, 2011, from http://www.ehow.com/how_4809745_homemade-stethoscope.html

This Project Idea is based on a collaboration with the 2011 Camp G.O.A.L.S for Girls at the Intrepid Sea, Air & Space Museum, New York, NY generously funded by the Motorola Solutions Foundation. The initial concept stems from work by Melissa Przyborowski from the Biomedical Engineering Department at Rutgers University as part of the Camp G.O.A.L.S. team.

Last edit date: 2011-10-26 12:00:00