SOUND VIBRATIONS
Introduction
A vibrating object creates disturbances in the air. These disturbances
or waves move through the air, eventually reaching our eardrums.
Our eardrums vibrate in response to the waves, enabling us to hear
sound. Sound waves must be conducted by some material: a gas
(such as air), a liquid, or a solid. Some materials are better
conductors than others. In this experiment, you will explore different
characteristics of sound as it is conducted by a variety of media.
Time Needed
35 minutes
What You Need
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8 drinking glasses
2 paper cups
meterstick
water, about 36 ounces (oz)
measuring cup
string, 3 meters long
pencil
partner
Safety Precautions
Please review and follow the safety guidelines.
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SOUND VIBRATIONS
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What You Do
1. Make a small hole in the center of the bottom of both paper
cups with a sharp pencil.
2. Measure 3 meters of string.
3. Pass one end of the string through each hole so that the string
runs between the cups from bottom to bottom (see Figure 1).
4. Tie a knot on the inside of each cup (see Figure 1).
paper cup
hole paper cup
knot
Figure 1
5. Working with a partner, take one cup each and stretch the string
taut between you.
6. Have one person speak quietly into the cup while the other
listens with the cup to his/her ear (see Figure 2).
speak
into cup
listen
with cup
string
Figure 2
7. Record your observations on the data table.
8. Pinch the string in the center and talk quietly into the cup while
your partner listens with the other cup (see Figure 3).
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SOUND VIBRATIONS
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pinch pinch pinch
near center far
Figure 3
9. Record your observations on the data table.
10. Repeat steps 8 and 9 pinching the string closer to you and
farther from you (see Figure 3).
11. Line up the eight glasses.
12. Fill the glasses with water, increasing the amount from one
glass to the next (see Figure 4).
glass
water
Figure 4
13. Tap each glass gently with a pencil.
14. Record your observations on the data table.
15. Try adjusting the amounts of water in each glass to produce a
musical scale.
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SOUND VIBRATIONS
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Data Table
Observation when talking and listening with paper cups:
Observation when talking and listening with paper cups and
pinching string in center:
Observation when talking and listening with paper cups and pinching
string close to speaker:
Observation when talking and listening with paper cups and pinching
string far from speaker:
Observation when striking filled glasses or “musical glasses”:
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SOUND VIBRATIONS
Observations
1. Which materials conducted the sound more effectively, the
string and the cup or the air in the room? How do you know?
2. What happened when you pinched the string? Why did this
happen?
3. What is the relationship between the amount of water in the
glass and its pitch when you strike it?
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SAFETY PRECAUTIONS
Review Before Starting Any Experiment
GENERAL
obtain your teacher’s permission for experiments
• Always
performed at school, and obtain your parent’s permission for
experiments performed at home, before attempting any
experiment.
all instructions for an experiment several times before
• Read
starting the experiment, and follow the directions exactly.
an experiment requires adult supervision, do not perform the
• Ifexperiment
unless you have an adult supervising you the entire
time you are performing the experiment.
your hands before the start of and after each experiment
• Wash
you perform.
• Keep your work area clean.
eat or drink while performing a lab experiment. Never taste
• Never
a substance used in an experiment unless you are told that it is
safe to do so.
aware of the location of safety equipment you may need in an
• Be
emergency, such as running water, an eyewash if you are at
school, and a fire extinguisher.
you are going outside, make sure you have permission to go
• Iffrom
your teacher and parent. Take a buddy with you, and dress
appropriately for the weather. Make sure you or someone who
accompanies you is familiar with the area, and bring along a
first-aid kit in case of an emergency.
• Never look directly into the Sun.
CHEMICAL SAFETY
wear goggles when working with chemicals, such as acids
• Always
and bases, and near heat sources like flames. If at all possible,
avoid wearing contact lenses when working with chemicals.
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SAFETY PRECAUTIONS
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any substance gets into your eyes, notify an adult (e.g., your
• Ifteacher
or parent) immediately, and flush your eyes with running
water for at least 15 or more minutes. Do not mix chemicals
unless you are told to do so by a teacher or parent.
• Never touch, taste, or smell chemicals unless instructed to do so.
• Keep chemicals in closed containers when they are not in use.
of all used chemicals properly. Do not pour any
• Dispose
chemicals or solids down the drain unless instructed to do so.
safety gloves and a plastic apron when handling chemicals.
• Use
If any chemicals spill on your skin, rinse the affected area with
running water for at least 10 minutes, and notify your teacher or
parent immediately.
precautions to avoid spilling chemicals. If a chemical spills
• Take
on any surface, notify your teacher or parent immediately to
assist with clean-up.
caution when using sharp instruments such as knives or
• Exercise
scissors. Always cut away from yourself, not toward yourself. If
you cut yourself, notify your teacher or parent immediately.
GLASSWARE
• Clean glassware when you are finished with the experiment.
careful when using glassware. If a piece of glassware breaks,
• Be
have an adult assist you in clean-up to avoid injuries from broken
glass. Never use broken or damaged glassware.
FIRE SAFETY
not heat glassware that is not completely dry. Do not pick up
• Do
hot glassware without heat-resistant gloves or tongs.
heating glassware, keep it away from yourself and from
• When
others.
not heat anything unless instructed to do so by a teacher
• Do
or parent.
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SAFETY PRECAUTIONS
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• Do not heat substances in a closed container.
an experiment, make sure that all heating sources are off
• After
and that all flames have been put out.
• Do not reach across such heating sources as flames.
you have long hair, tie it back, out of the way. Do not wear
• Ifclothing
with loose sleeves, scarves, bows, ties, or anything else
that may hang into a fire. Do not wear long earrings.
ELECTRICAL SAFETY
• Do not touch electrical equipment when your hands are wet.
not plug many electrical devices into one outlet or use an
• Do
extension cord.
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