Lesson 3: Safe and Sound
Time Required: One 40-minute class period
Materials: Safe and Sound student worksheet, pipe cleaners (10 per student), radio or CD player
This lesson helps students understand the importance of protecting their sense of hearing through a listening experiment.
1. Begin by giving a short True/False quiz:
A. Exposure to excessive loud noise can cause hearing loss. (True: Loud sound destroys the sensory fibers in the inner ear that are responsible for converting sound waves into electrical impulses. Once 25% to 30% of these cells disappear, you begin to experience hearing loss.)
B. One in 5 American teenagers suffers from some type of hearing loss. (True)
C. It's safe to listen to your iPod at maximum volume for 90 minutes a day. (False: Experts recommend no more than 90 minutes a day at 80% volume.)
D. You should wear earplugs when mowing the lawn or going to rock concerts. (True: Noise above 85 decibels can cause hearing damage. Lawn mowers = approximately 90 decibels and rock concerts can reach up to 140 decibels.)
E. Damaged hair cells can grow back over time. (False: Damaged hair cells cannot recover.)
F. Hearing loss usually occurs gradually over a period of years. (True)
2. Distribute the Safe and Sound student worksheet. Walk students through Part I. Review the illustration with your class and demonstrate how loud sounds damage delicate hair cells of the inner ear with this simple activity.
- Distribute 10 pipe cleaners to each student, and ask that they hold the pipe cleaners upright in their fists, as though they're holding flower stems in a bouquet. Explain that the pipe cleaners represent cilia, the delicate projections, or "hairs," inside the cochlea. Students should place the flat palm of their opposite hand atop the pipe cleaners.
- Turn on the radio to a low volume. Cue students to use the flat palm of their opposite hands to wave the pipe cleaners gently back and forth. Tell them that this movement represents the cilia moving in response to the vibrations from a sound wave.
- Turn the volume up, and move around the room with the radio and CD player. As the music gets louder and closer, students will wave their hands more vigorously to mimic the action of loud sounds on the cilia.
- Stop the music and ask students to observe their pipe cleaner bouquets. What do they see? Explain: The pipe cleaners became bent from the energetic movement of the loud sounds. The same thing happens to the cilia in our ears.
- Ask students to try to straighten the pipe cleaners. They'll find it's impossible to return them to their original appearance. Tell them that the same is true of cilia. Once cilia are damaged, they cannot be repaired.
3. If time permits, encourage students to complete Part II in class or assign as homework. When they've finished Part II, discuss their findings as a group.
Have students create a visual collage of sounds from magazine clippings and photos to further develop their appreciation of the beauty of sounds. Collect all of the collages to create a Listen Carefully-themed bulletin board.