Blaine W. Greenhalgh, American Fork Junior High, American Fork, UT
SEEING SOUND & SONAR
Appropriate for grades 7-8.
OVERVIEW: This activity is used to introduce ocean floor mapping
and features. It is important for students to understand that one
can "see" in many different ways. The activity will help students
grasp how one can see with sound waves. It will also introduce
them to the vast amount of information contained in sound. The
intent is to understand how sonar can help science see the ocean
floor. The concept of seeing with all kinds of waves, not just
light, can be extended to many areas of science--i.e. seismicity
and earth structure, planetary surfaces and radar, etc. This is a
standard activity, but with a distinctive twist.
PURPOSE: This activity will give students practice in making
inferences. It will illustrate that high amounts of information
is contained in all types of waves, not just light waves. It is
helpful in building a conceptual understanding of sonar radar and
other means of investigating our world.
OBJECTIVES: Students will be able to:
1. Practice making inferences based on observations.
2. Categorize (list) the kinds of information contained in sound
waves.
3. Explain why light is not the only way one can "see" the
universe.
ACTIVITIES: Introduce the activity to the students by saying:
"How can we know what is on the ocean floor if it is always dark?
How can one see the surface of Venus if the planet is always
covered with clouds? These are common questions that need
answers. This activity will help you understand how one can "see"
with waves other than light."
1. Hold up two stones, one polished and one rough. Ask, "Which
is smooth, which is rough?" Accept student responses. Ask,
"How do you know this stone is smooth, did you touch it?"
Bring into your discussion the idea that texture, something
we normally experience by touch, can also be determined by
analysis of light waves. (Student may ask why the polished
rock is shiny and the other one dull. If so, a brief
discussion would be helpful here.)
2. Ask students to take out some note paper and make six columns
half way down the paper. Label each column "Box 1", "Box 2",
etc. When everyone is ready, instruct students to list what
they hear as you shake each box. Encourage them to describe
the sound, not to attempt to name the objects.
Shake the first box. Have students describe what they hear.
They should record what they hear on their paper. Repeat for
each remaining box. Move among the students so everyone can
hear and you can check their work. Students may have
difficulty describing sounds--provide help as needed by
asking these questions:
a. Are there many objects or a few?
b. Is the object as big as the inside of the box or
smaller?
c. Is the object hard or soft?
d. Does it slide, tumble or roll?
e. Does question e. tell you anything about the shape?
If so, what?
f. If the object uniform or does it roll one way and tumble
the other?
g. Does it sound like metal, glass, plastic, etc.?
h. Is it heavy, light or in between?
After all boxes have been examined, ask student to share
their descriptions.
As students share their responses, build list of terms on
the chalkboard. After the last student, ask the class to
categorize the terms. Students should see that some terms
describe number; some describe size; some, shape; some
hardness; some mass and some composition.
Ask the students to categorize all the terms they used in
describing the sounds. Point out the wide range of
information they obtained from just sound waves. Check each
categories. The students should do this at the bottom of
their columns.
Tell the students that all the objects in the boxes are
common household objects. Instruct them to make inferences
about what the object in each box is. Ask for student
responses. Point out that one can interpret sound waves in
several ways. No one interpretation is necessarily right.
After discussing each box, open the box and let them check
their inferences.
Point out that they were able to interpret sound waves to see
something hidden from view. Explain that sonar is used to
see the hidden world of the ocean floor. Show a depth chart
or echo sounding profile if available. Explain that sonar
was not the first way science tried to see the ocean floor,
but is the best way we have available to us today. Explain
that the next time they are going to test their ability to
"see" an "ocean floor". Introduce the FOR SEA activity,
"Worlds Smallest Ocean".
RESOURCES/MATERIALS NEEDED:
2 stones, 1 polished, 1 rough.
6-10 common household items.
6-10 boxes with lids (boxes that nuts and bolts come in at
the local hardware store are excellent).
Ocean floor profile poster of echo sounding strip chart
(optional).
TYING IT ALL TOGETHER: This is a general activity, the importance
is to help students use all their senses to learn of the world
around them. It also helps students understand the wide range of
information obtainable from all kinds of waves. Much of the
success with this approach comes from teacher enthusiasm and
motivation. Help the kids be curious about the unseen by your own
interest.
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John Kurilecjmk@ofcn.org