Activity 2 Overview
Youngsters will explore how sound travels by conducting a range of
experiments with paper cup telephones.
Estimated Time and Age Level
Advance Preparation: 20 minutes
Activity: One 40-minute session
(Ages 8-12)
Materials
(Per Team)
2 paper cups
6 meters (20 feet) of waxed dental
floss or colored fishing line
2 paper clips
paper and pencil
Preparation
Divide the group into teams of two
children each. Make sure that the area where youngsters will test their
phones is fairly quiet.
Cut the floss or line into roughly
6-meter (20-foot) sections. If the children are younger than eight, you
might want to provide assistance where appropriate as they assemble their
paper cup telephones.
Set out the materials in a central
location.
Procedure
Set the stage for the activity
by asking children how they think sound is traveling from your mouth to
their ears. If (following from their experiences with Activity
1) they suggest that some kind of sound vibration is moving through
the air, ask them to consider how sound vibrations could do this. Suggest
that they explore how sound moves by conducting some simple experiments
with a classic paper cup telephone.
To begin their experiments, children
should create a "baseline" by standing a measured distance (six
meters or 20 feet) from their partners and whispering into their cups.
Can their partners distinguish the words? Ask them to keep track of their
findings by recording their observations.
Children should begin making their
telephones by using a pencil to poke a hole in the bottom of a cup. (They
should stick the pencil right through.) Then they can tie one end of the
floss or fishing line around a paper clip. The inner "loop" of
the paper clip should then be inserted through the hole from the outside
of the cup so that it is clipped securely to the circular bottom of the
cup. Have children repeat this process using the other end of the line
and the second cup.
Now youngsters should return to
their "baseline" distance. Each child can take turns placing
the cup against one ear while his or her partner whispers into the cup
at the other end of the line, always making sure that the line remains
taut. Youngsters should now be able to hear their partners' voices resonating
in the cups against their ears. Ask them to describe their results and
to follow up with their own questions (and possible explanations) about
what happened.
For example:
How are the sound vibrations getting
from one cup to the other? (They travel through the line.)
After the vibrations get to the
cup at the end of the line, what might they be doing to the bottom of the
cup? (They cause it to vibrate, moving the air inside the cup in the same
pattern that was created by the original sound.)
Now challenge the youngsters to
think of different experiments to try with their telephones. For example,
they might find out whether or not their telephones will work when their
lines are stretched through a closed door, or when their fingers are pressed
against the bottom of the cup. Before they try an experiment, you might
want to have them write down the procedure and the expected results. After
trying the experiment, they can record their results and try to explain
why or why not their prediction came true.
Bring students back to the original
question. Ask them how they can use what they've learned with the paper
cup telephone to explain how sound travels through air. If necessary, move
the discussion along by giving children this hint:
When people talk to each other,
the space between them is not empty; it's filled with air. Air is a substance
just as the dental floss or fishing line between the cups is a substance.
What does this suggest about how sound travels? (Sound needs a substance
through which to travel.) Relate the talking-in-space
anecdote, if you like.
Assessment
To see how well your young scientists are understanding the properties
of sound, challenge them to explore the properties of their paper cup telephones
further by designing new experiments. If they get stuck, suggest the following:
Try using your telephone with
a sagging line between the cups. Does it work? Why or why not? (It won't,
because the pulling and pushing action of the diaphragm--the cup bottom--in
response to your voice's sound waves will not transmit efficiently along
a sagging line.) Might it work if you used copper wire instead of fishing
line or dental floss?
Try using your telephone with
someone holding the line in the middle. Does it work? If not, where are
the vibrations going? (It doesn't work because the vibrations are partly
diverted by the person holding the line, weakening the signal that reaches
the "receiving" paper cup.)
Extension
Older students could use their paper cup telephones to explore another
important quality of sound--that it travels at different speeds through
different media. All they'll need to do is replace the line between their
cups with one that's three times as long. Then ask them to stand as far
as the line will allow, again making sure that the line is taut. As one
partner puts the cup to one ear, the other can shout while holding the
cup on the other end of the line about six inches in front of his or her
mouth. The "receiver" should hear the shout first through the
ear covered by the telephone and then--an instant later--through the other
ear.
Leave it to them to hypothesize why the shout reached one ear before the
other. (Sound travels faster through solids than through gases.)
This activity has been copied, with permission, from the National Science Foundation server to ours, to allow faster access from our Web site. We encourage you to explore the original site.