Enrichment 5-1: Teacher Activity Notes
Building a Model of the Ear
Summary Students review and discuss sound energy. Demonstrations of the movement of waves using a rope and water help students visualize sound waves. Students review and discuss the structures of the human ears and how they help us hear. They construct a model of the human ear and use it to explain how to care for and protect the ears.
✓ identify the parts of the ear.
✓ state the function of each part of the ear.
✓ describe how loud noises can cause ear damage.
✓ describe how to care for and protect their ears from damage.
- Resources 1 and 2
- Activity Report
- 2 Water balloons or one balloon and a latex glove; Juice container (empty); Scissors; Cork; Balloon; String or rubber bands; Push pin or thumbtack; Plastic or rigid paper cup
- Resource 3
- Activity Report Answer Key
- Beaker (or petri dish bottom or glass pie plate); Water; Eyedropper; Overhead projector; Saber saw (variable speed electric); Rope; Resonator (refer to Resource 3 for materials and construction)
Obtain all student and teacher materials.
Allow ample time to collect necessary materials (i.e., juice bottles, saber saw, constructed resonator.)
Consider preparing an ear model in advance to use as a reference after students complete their models.
Remind students to use their brain models from previous activities to refresh their memories about the brain parts and their functions: Activity 2-1: Big Brain on a Stick and Activity 2 -2: Thinking Cap.
Fill the balloons with water while they are inside the juice container as follows: Find a water spigot on which you can place and hold the neck of the balloon. When the filled balloon almost reaches the bottom of the juice container, quickly pull off the neck of the balloon and tie it. Do this ahead of time. You might want to wear a plastic apron.
Approximately one to two 50-minute class periods
Music Explore tonal variations with different musical instruments.
Social Studies Investigate local regulations governing noise pollution.
Health Research hearing loss and compensations available for those physically challenged with hearing impairment. Research ear protections required for various careers.
Prerequisites and Background Information
Review the concept of sound energy with students.
All materials should be available as listed on student Activity Guide.
Recommend juice bottle (16 oz.-refer to Resource 1).
Encourage students to investigate and report on animal hearing.
When doing this activity with more than one class, the first class can keep the “inner ear”-the juice bottle with the water balloon in it-for the classes that follow.
Use the model of the ear and written responses on the Activity Report to assess if students can
✓ identify the parts of the external ear, middle ear, and outer ear.
✓ explain how the function of each part of the ear enables humans to hear.
✓ demonstrate how sound travels through the different parts of the ear, how the cochlea acts as a resonator, and how the brain receives information from the ear.
✓ explain how to care for and protect their ears.
Enrichment Activity 5-1: Building a Model of the Ear – Activity Report Answer Key
- Sample answers to these questions will be provided upon request. Please send an email to email@example.com to request sample answers.
- What is the function of the human ear?
- Describe your ear model.
- Can you think of other materials that you can substitute for materials used in this model?
- Use your model to trace sound waves from their point of entry into the external ear until they are received by the brain. Include in your answer the parts of your model as they correspond to the parts of the human ear.
- Could the ear function properly if one of its parts were damaged or missing? Provide an example to support your answer.
- Describe two ways your ears could be damaged. How could you prevent this damage from happening?
Enrichment 5-1 Activity Guide: Building a Model of the Ear (Student Reproducible)
Do you know how your ear works? In this activity you make a model showing how your ears work.
- Resources 1 and 2
- 2 water balloons or one balloon and a latex glove
- Juice container (empty)
- String or rubber bands
- Push pin or thumbtack
- Plastic or rigid paper cup
Step 1 Using Resource 1 as a guide, build a model of the outer ear. The outer ear includes the flap on the side of your head and a bony canal at the end of which is the eardrum. Your plastic cup represents the ear canal. Cut the bottom out of the cup. Then tie a cut balloon or a piece of latex glove over the cut end to represent the eardrum.
Step 2 Using Resource 1 as a guide, add to your model of the outer ear to include the middle ear. The middle ear includes the space behind the eardrum and the three small bones (hammer, anvil, and stirrup) that transmit eardrum movements to the oval window. In your model, the cork represents the bones of the middle ear.
Step 3 Using Resource 1 as a guide, modify your model to include the inner ear. The inner ear includes a spiral hole in the skull, which contains the cochlea. The juice container represents the canal in the bone. And the water balloon represents the fluid in the inner ear. Place your finger over a cut part of the juice container, resting against the water balloon, to represent the cochlea. Pressure-sensitive nerve endings in your fingertips represent hair cells. Sensory pathways to your sensory cortex represent the auditory nerve and temporal lobe. Compare your completed model of the ear with Resource 2.
Enrichment 5-1 Resource 1: Building a Model of the Ear (Student Reproducible)
Building the external ear
Cut the bottom from the plastic cup and stretch a piece of balloon over it. Tie or tape a rubber band over the balloon to make the eardrum at the end of the external ear canal.
Building the middle ear
Push the thumbtack through the balloon from inside the cup into the cork. The cork moves in and out as the drum moves in and out. The cork represents the chain of three bones connecting the eardrum with the inner ear.
Building the inner ear
Cut a hole as big as your fingertip in the side of the plastic juice container. Put an empty balloon in the container and fill it with water from a faucet. Tie the balloon closed.
Seeing your ear working
Insert the cork through the mouth of the juice container and hold one finger against the water balloon.
Press the finger in the cup and feel the pressure in the water balloon. Pressure waves in the fluid are converted to impulses in the acoustic nerve. The impulses from your finger felt in your brain as a pressure are analogous to the impulses from your cochlea perceived by the temporal lobe as sound.
Enrichment 5-1 Resource 2: Building a Model of the Ear (Student Reproducible)
Enrichment 5-1 Resource 3: (Teacher Guide) - Building a Model of the Ear
1. Making a Wave (Demonstration)
Place a beaker or petri plate bottom containing a small amount of water in it on an overhead projection. Using an eyedropper, add 1 or 2 drops of water into the center of the container. Notice the concentric rings (waves) start in the middle and reflect off the sides back toward the center. Use this demonstration to discuss sound reflections such as echoes and concert hall acoustics.
You also can use a slinky to show compression waves and reflection.
2. Making a Wave with a Rope (Demonstration)
To see what a wave looks like, we'll make one stand still so you can see the parts using 15 feet of string or cord and a variable speed electric saber saw. Take the blade out and screw the blade-holding screw tight. Tie one end of the cord to the blade holder and tie the other end to a fixed object-a table leg will do. Turn on the saw and step back to tighten the string.
Each in and out movement of the saw starts a wave traveling down the cord. The wave reflects back on itself at the fixed point. The reflected wave returns to the saw and joins with newly formed waves to form a standing wave that seems not to move along the cord. How many waves can you form on the string at the same time? Some parts of the string appear to stand still. What are these points called? [Nodes]
- Speed of the wave along the cord depends on tension in the cord.
- A wave travels one wavelength in one period of the wave.
- The faster the in-and-out motion of the saw, the shorter the time between the waves (the greater the frequency) and the shorter the wave lengths.
3. The Cochlea as a Resonator
Let us see a resonator working because the organ of Corti behaves a bit like one. Resonance is when a small repeated vibration causes a larger vibration in the resonating body.
Musical instruments, the cochlea of the ear, bridges in storms, and buildings in earthquakes act as resonators. If you vibrate an object near one of its natural frequencies, its motion may grow much larger. This demonstration shows again that waves carry energy.
To do this one yourself, you'll need three 14-inch wooden dowels, one 18 inches long, one 24 inches long, and one 30 inches long. You'll also need one 38-inch dowel about 2 feet long, 4 superballs, tennis balls, or lumps of clay, and one 2′′×4′′ piece of wood about 2 feet long, a drill, and some glue.
Drill 4 holes equidistant along the 2′′×4′′ piece of wood. Make the first hole slightly less than 38′′ and the other 3 slightly less than 14′′. Tap or glue the dowels in the holes. Drill holes in the superballs and stick them on the ends of the dowels.
Hold the 2′′×4′′ at each end and slide it back and forth on a table. What happens?
Sticks will sway back and forth in a wavelike motion.
It is like pushing a swing. Each push adds amplitude to the swing's natural frequency. Try a different frequency. What happens?
Each push changes how far and how fast the sticks sway.
Enrichment 5-1 Activity Report: Building a Model of the Ear (Student Reproducible)
Answer these questions:
1. What is the function of the human ear?
2. Describe your ear model.
3. Can you think of other materials that you can substitute for materials used in this model?
4. Use your model to trace sound waves from their point of entry into the external ear until they are received by the brain. Include in your answer the parts of your model as they correspond to the parts of the human ear.
5. Could the ear function properly if one of its parts were damaged or missing? Provide an example to support your answer.
6. Describe two ways your ears could be damaged. How could you prevent this damage from happening?