Now Hear This!
Students investigate their hearing range.
Killer whales have a well-developed, acute sense of hearing. They have responded to tones within the frequency range of about 0.5 to 100 kHz. Their peak sensitivity is about 15 kHz. Humans can hear sounds within the frequency range of about 0.02 to 17 kHz.
1. Explain to students that killer whales, like other dolphins, have very good hearing. Hearing is one way living creatures learn about their surroundings.
2. Tell students that all this week they will be taking part in a hearing experiment. Show them the dog whistle, bell, metal clicker, bike horn, and two plastic soda bottles, and make a noise with each. (Hit the two plastic soda bottles together.) Explain that sometime during recess every day, you'll use one of the objects to make a noise on the playground. Ask them to make a hypothesis, a guess, which instrument will be the easiest to hear, and which will be the hardest to hear. Record their hypotheses.
3. Tell students that if they hear the noise, they should take note of which sound they heard and where they are on the playground. Encourage students not to discuss what they heard with others in their class, since this might affect the experiment by giving the answer to someone who didn't hear the noise.
4. When students come back to the classroom after lunch, have them whisper in your ear what sound they heard. Make a mark on the board for each student who heard the noise (don't tell them what the noise was, or by the last day they'll know which instrument is left). Leave the marks on the board, labeled with the day of the week.
5. Ask a few of the students where they were positioned on the playground, and tell them where you were. Did people far from you hear the noise?
6. On the last day, tell students what instrument was used to make noise each day. Ask students which noises were easiest to hear. Which were most difficult? Compare their answers with their hypotheses. What things affect what they heard? (Where they were on the playground, how loud the noise was, etc.)
For more information on killer whale hearing, visit Killer Whales
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