Do Loud Noises Affect Heart Rate?

Grade Levels: 5 - 7

The human body is a marvelous creation. One of its really awesome features is its reflex system. Reflexes are sort of an automatic safety response system in your body, and they work to protect you from harmful situations.

Think about a time when you accidentally touched something hot, like the kitchen stove or an iron. Before you had time to think about what was happening, you had jerked your hand away from the hot -surface. That immediate response was caused by a reflex.

The heat and pain sensors in your hand sent a message to the spinal cord, which sent a message to the arm and hand muscles. That message was something like, "Yikes, get me out of here!"

While all that was going on, a message was on its way to your brain, allowing pain to register after you had already pulled your hand away.

The brain is the control center of the human body. It communicates via chemical messages with the different systems that make up the body, such as the muscular, digestive, and circulatory systems. When your reflexes kick in, they activate the nervous system, which relays a message to the muscular system, telling it to "Move!"

Other things happen in your body as well when your reflexes are activated. Think back on some of your own experiences and think how you felt after you had a real scare or did something that put yourself in harm's way.

Can you remember feeling your heart pounding? Your pulse racing? Maybe your face felt very hot, or you even started shaking involuntarily. Your body reacts in many ways that are not within your control.

In this project, you're trying to find out whether loud noises affect the rate at which a person's heart beats. Form a hypothesis by thinking about some of your own experiences, and using your observations and research.

You'll need to get several people to agree to participate in your experiment. The first thing you'll do is determine the resting heart rate of each person with whom you're working. To do that, you'll need to locate the pulse point on each person's wrist. That's where you can feel the beating caused by regular contractions of the heart.

Record the number of beats you feel for 10 seconds, and then multiply that number by six. That will tell you how many times the person's heart beats in one minute, while at rest. Heart rate varies throughout the day in most people. A resting heart rate may be 70 beats per minute, while, during strenuous exercise, it could increase to 160 or 170 beats.

There are several ways you could conduct this experiment. One would be to get someone to be your assistant, and have him or her sneak up behind the person whose pulse you've just taken and drop a large, heavy book on the floor. The unexpected sound should be enough to startle your subject, after which you can immediately check the heart rate again to see if it's changed.

Check the person's pulse every minute for three minutes to see if the heart rate changes. If he or she was startled by the noise and the heart rate increased, perhaps it will decrease again as the effect of the noise wears off.

If you don't have someone to help you, you can make a loud noise yourself once you've established the resting heart rate. Be a little creative with this experiment.

This experiment will work best if you repeat it several times with different people as your volunteers. Check to see if you notice any patterns in the heart rates of the different people. Did everyone's heart react the same way? Was the age of the person a factor?

The more data you can collect concerning the effect of loud noise on heart rate, the more reliable your results will be. Repeating the experiment several times will give you the data you need to either prove or disprove your hypothesis.

Excerpted from The Complete Idiot's Guide to Science Fair Projects © 2003 by Nancy K. O'Leary and Susan Shelly. All rights reserved including the right of reproduction in whole or in part in any form. Used by arrangement with Alpha Books, a member of Penguin Group (USA) Inc.

To order this book visit the Idiot's Guide website or call 1-800-253-6476.

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