Bats and Echoes

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SUBJECTS

life sciences, physical sciences, language arts



GRADES

K-8



CONCEPTS

sound production
and receiving as
an adaptation



DURATION

one or two
class periods




[graphic]

text link

[definition]

graphic link


You may print this activity
for educational use.

Objective

Before their visit, students will learn to ... make and listen to echoes like a bat.

Background Information

Sounds are created when something vibrates and your ears pick up the vibrations. Many animals are much better than humans are at hearing sounds, and a few animals hear so well that they can "see"in the dark.

Bats [graphic] are probably the best at using sounds to see. They hunt at night and most hunt for flying insects [definition]. To find food, bats use echoes. An echo is a sound that's repeated as the sound waves reflect off a surface. A bat's echolocation [definition] system produces a burst of high-pitched sounds as the bat flie s. Those sounds bounce off objects and from the returning sounds (echoes) a bat can tell if the object is a rock or a moth, how big it is and how far away. Take a look at most bats and you'll probably find big ears for receiving echoes.

Humans developed something like echolocation when they created sonar during World War II. Sonar is an apparatus that transmits high-frequency sound waves through water and registers the vibrations reflected back from an object, such as a submarine or the ocean bottom.

This activity gives your students a closer look at how echoes are created.

Activity

Materials

For each pair of students:

  • A watch that ticks.
  • A large piece of cardboard or hardboard.
  • Two paper towel tubes.
  • Other objects that make soft sounds: a chime, a baby rattle, clicking fingers, a whisper. Be creative.

QUESTIONS TO BEGIN


Where do sounds come from?

What do you hear with? How do your ears work?


Procedure

  1. Have students get into teams of two.
  2. Give each pair a piece of strong cardboard or hardboard, a ticking watch and two paper towel tubes. The cardboard will be used to "bounce" the sounds of a ticking watch.
  3. Start by having students listen through a tube to the ticking watch. Have them record what they hear.
  4. Have one partner hold the watch at one end of a paper tube as he or she directs the other end of the tube toward the sounding board (cardboard).
  5. Have the other partner cover one ear and hold a paper towel tube up to the other ear. Direct the open end of the tube toward the sounding board.
  6. Experiment with different positions of the tubes.
  7. Experiment with different objects that make soft sounds.
  8. Have students write down their observations.

QUESTIONS TO CLOSE

When you first listened to the watch, what effect did the paper tubing have on the sound of the watch?

What happened to the sounds when you directed the paper tube at the sounding board and listened to the board? Did it sound the same as when you listened to the watch through the tube?

What is an echo? How are echoes created? Do you think the sounds bouncing off the sounding board are echoes?

How do bats use sounds to hunt in the dark? (They use echoes.) Why do they have such large ears?

How does bat echolocation work? How does sonar work? What are the similarities and differences between echolocation and sonar?

Extensions / Variations

Have your students practice pinpointing the location of sounds. Have a student sit in a chair in the middle of the classroom and blindfold him or her. Have other students quietly sit in a circle around the chair, but at different distances. P oint to one of the students in the circle and have him or her snap fingers. Have the student in the chair point to the location of the sound and tell you if the sound is close or far away. Try a few more times. Then change students.

Adapted from

Vivian, C. Science Experiments and Amusements for Children. New York, Dover Publications, Inc., 1963.

Additional Sources

Parker, Steve. How the Body Works. Pleasantville, NY: Readeršs Digest, 1994.