How Your Brain Understands What Your Ear Hears
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How Your Brain Understands What Your Ear Hears

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Teacher's Guide

Lesson 4—Elaborate

A Black Box Problem: How Do I Hear?

At a Glance

Figure 4.1
Figure 4.1.
Sound energy must be converted into a form that can be processed by the brain.

Overview

Students assemble a diagram of the hearing pathway using information about its parts and their functions, describe how sound is represented at various points along the pathway, and predict the changes in hearing that might result from specific changes to the pathway.

Major Concepts

The hearing pathway processes sound in a series of steps that involve different structures within the ear. Hearing requires the passage of vibrational energy from one medium to another, as well as its conversion to electrical energy in the form of nerve impulses. Transduction, which occurs in the cochlea, is the conversion of vibrational energy to electrical energy. Damage to specific parts of the hearing pathway results in predictable changes in hearing. The interpretation of what one hears occurs in the brain.

Objectives

After completing this lesson, students will

Teacher Background

Consult the following sections in Information about Hearing, Communication, and Understanding:

  1. 3.4 Perception of sound has a biological basis
  2. 4.6 Cochlear implants

In Advance

Web-Based Activities
Activity Web Version?
1 Yes
2 No
Photocopies
Activity 1 Master 4.1, The Mysterious Black Box (Prepare an overhead transparency.)
Master 4.2, A Few Questions (Prepare an overhead transparency.)
Master 4.3, Black Box Cards (Make 1 set of 8 cards per team for print version.)
Master 4.4, The Bell Card (Make 1 copy for print version.)
Activity 2 Masters 4.5, Understanding Form and Function (Make 1 copy per team.)
Materials
Activity 1

a small bell
a lamp without a shade
a computer with Internet connection and sound card

Activity 2 no materials (except photocopies)

Preparation

Activity 1 (print version)
To prepare the Black Box Cards, make copies from Master 4.3 and cut the cards along the dotted lines.
Activity 2 (print version)
No preparations are needed except photocopying.

Procedure

Activity 1: The Mysterious Black Box

Web activity icon
National Science Education Standards icon
Content Standard A:
Think critically and logically to make the relationships between evidence and explanations.

Content Standard B:
Energy is a property of many substances and is associated with heat, light, electricity, mechanical motion, sound, nuclei, and the nature of a chemical.

Teacher note
The following procedure describes how to conduct the Web-based version of this activity, the preferred form of instruction. Instructions for conducting the alternative print-based version follow the Web-based instructions.

  1. Explain to the class that they will use a Web-based activity to explore the hearing pathway and the process by which it converts sound waves into signals that can be understood by the brain.

If you feel that your students would benefit from a more extensive introduction to the activity, consider having the class proceed through Steps 1–4 from the print-based procedure.

  1. Explain to the class that they will view eight pictures, each representing a different part of the hearing pathway. As they position the cursor over each picture, they can read a brief description of that part’s role in the hearing process. The students’ task is to arrange the pictures in their proper sequence in the hearing pathway.

After students arrange the pictures in a sequence, they can test themselves by clicking on the “Try it” button. If a mistake has been made, only those pictures that are in the correct order remain where they are, while those that are incorrect move back to the starting position for the student to try again. When the correct sequence is assembled, the hearing pathway fades away and a cartoon animation appears. The animation shows how the sound is represented along the hearing pathway. A sound is heard only after the electrical impulse reaches the brain.

  1. Instruct students to proceed to http://science.education.nih.gov/supplements/hearing/student and click on “Lesson 4—A Black Box Problem: How Do I Hear?”

Students should pay particular attention to the introduction, which includes a cartoon that depicts how sound waves travel through the hearing pathway and introduces the term transduction. Transduction is the process by which sound is converted into a form that the brain can understand.

As students perform this activity, circulate around the room and ask each team to explain why they put the pictures in the order they did.

Figure 4.2. Drawing of pinna  Figure 4.2. Drawing of ear canal  Figure 4.2. Drawing of eardrum  Figure 4.2. Drawing of ossicles
Figure 4.2. Drawing of cochlea  Figure 4.2. Drawing of organ of Corti  Figure 4.2. Drawing of auditory nerve  Figure 4.2. Drawing of brain
Figure 4.2.
The parts of the human hearing pathway in their proper sequence.

print activity iconAlternate version of Activity 1 for classes without access to computers:

  1. Turn on the lamp and ask the class how the light bulb produces its light.

Student responses will vary. Direct the discussion to how electrical energy flows through a wire to the light bulb filament where light, as well as heat, is generated.

  1. Write the word “transduction” on the board and explain that it refers to the process by which energy is converted from one form into another. Ask students if they can name other examples of transducers.

Students’ examples may include flashlights, microphones, photocells, stereo speakers, engines, and other such devices. If no one mentions a biological system, ask the class if living things can transduce energy. Examples of biological transduction may include the process of photosynthesis, which converts light energy into chemical energy, or the process of respiration, which converts chemical energy into mechanical energy.

Figure 4.3. Lamp  Figure 4.3. Microphone  Figure 4.3. Green plant
Figure 4.3. Examples of transducers.

National Science Education Standards icon
Content Standard B:
Energy is a property of many substances and is associated with heat, light, electricity, mechanical motion, sound, nuclei, and the nature of a chemical.

Content Standard A:

Identify questions that can be answered through scientific investigations.
  1. Display an overhead transparency made from Master 4.1, The Mysterious Black Box. Ask students to describe the picture and to identify the question it raises.

Figure 4.4
Figure 4.4.
The Mysterious Black Box.

Guide the discussion so that students ask a focused question pertaining to hearing, such as, “What happens inside the hearing pathway to allow sound to be heard in the brain?”

Ask students to rephrase the question to include the concept of transduction: “How is sound converted to a signal that the brain can understand?”

Students should understand that the black box represents the parts of the hearing pathway that they cannot see. You may wish to explain that scientists are often able to observe only the beginning of a process and its outcome but not the events that lead from one to the other. The challenge of the black box is to identify and describe all of the intermediate steps.

  1. Display an overhead transparency made from Master 4.2, A Few Questions. Uncover the questions one at a time as the discussion proceeds. Invite students to speculate as to what happens inside the black box of hearing.

Sample answers to Master 4.2, A Few Questions, follow:

Question 1. What do the lines between the bell and the ear indicate?

The lines depict sound waves (vibrational energy) moving from the bell to the ear.

Question 2. What is a sound wave?

A sound wave is a wave of vibrational energy (or a pressure wave) that moves through a medium such as air or water.

Question 3. Do vibrations reach all the way into the brain to let us hear sound?

This question is analogous to the example of the lamp as a transducer. Just as light doesn’t travel through wires to the light bulb, students should recognize that the actual vibrations do not travel to the brain. Instead, the ear converts the vibrational energy of sound into electrical energy, the energy of nervous impulses. To help students formulate this answer, you may wish to ask the analogous questions, “Does the light that enters our eyes go all the way to the brain?” and “When you touch someone’s skin and they feel it, does the ‘touch’ go all the way to the brain?”

  1. Explain that in this activity, students will construct a flow chart that shows what happens inside the black box of hearing. Hold up a set of Black Box Cards and explain that each team will receive a set of eight cards that provides information about the structures and functions of the hearing pathway.

Each card includes a picture of a part of the hearing pathway and a brief explanation of the part’s function. The team’s first challenge is to assemble the cards in the correct order so that the sound of the bell will be heard in the brain.

National Science Education Standards icon
Content Standard A:

Think critically and logically to make the relationships between evidence and explanations.

assessment icon
Assessment:
As students perform this activity, circulate around the room and ask each team to explain why they put the pictures in the order they did. If a team struggles to place the pictures in the correct order, ask the students various guiding questions to help them overcome their difficulties. If necessary, point out to the team that their sequence is correct up to a certain point.
  1. Organize the class into teams of two or three students. Distribute a set of Black Box Cards to each team. Announce that teams have 10 minutes to put the cards in the correct sequence. During that time, while students are working, you will circulate through the room with a “testing device” (hold up the large Bell Card and the bell). Explain that when a team decides it has assembled the pictures in the proper order, you will use the device to test the sequence.
  2. To test each team’s pathway, give one team member the Bell Card and ask him or her to place it at the start of the flow chart. The Bell Card illustrates the vibrations produced as the bell rings. After the student puts the Bell Card in position, have the students explain what happens to the sound as it is transmitted through the hearing pathway. If the students’ sequence of cards and explanation of events are correct, ring the bell to indicate that the impulse reached the brain, where it is interpreted. If the pathway is not correct, do not ring the bell and ask the team to try again.
  3. Write the names of the hearing-pathway components on the board as follows:
  1. tympanic membrane (eardrum)
  2. ossicles (bones of the middle ear)
  3. pinna (outer ear)
  4. cochlea
  5. brain
  6. auditory nerve
  7. organ of Corti (containing hair cells)
  8. ear canal

Instruct the teams to match the letter that corresponds to each component of the hearing system with its image.

Figure 4.5 provides a visual guide for the correct order of Black Box Cards.

Figure 4.5. Drawing of pinna  Figure 4.5. Drawing of ear canal  Figure 4.5. Drawing of eardrum  Figure 4.5. Drawing of ossicles
Figure 4.5. Drawing of cochlea  Figure 4.5. Drawing of organ of Corti  Figure 4.5. Drawing of auditory nerve  Figure 4.5. Drawing of brain
Figure 4.5.
The Black Box Cards in their proper sequence.

As you review the functions of the components of the hearing pathway, draw attention to each part’s name. After you have reviewed all eight components, introduce the terms “outer ear,” “middle ear,” and “inner ear,” and ask students to place these labels at the appropriate points in the sequence of pictures that depicts the hearing pathway. Ask students to name the parts of the hearing pathway that are not part of the ear, such as the auditory nerve and the brain.

Figure 4.6
Figure 4.6.
The hearing pathway showing the outer, middle, and inner ear.

  1. Before proceeding, construct the hearing pathway on the board so that students may refer to it while engaged in Activity 2.
National Science Education Standards icon
Content Standard C:
Living systems at all levels of organization demonstrate the complementary nature of structure and function.

Activity 2: Understanding Form and Function

  1. Review transduction with the class. Make sure students understand that transduction is the conversion of energy from one form into another. Ask the class where in the hearing pathway transduction occurs.

Students may respond that transduction occurs either in the cochlea or in the organ of Corti. If there is confusion, help students understand that the organ of Corti is found within the cochlea. Explain how the hair cells are organized in the cochlea, how they detect the pressure waves moving through the cochlea, and how they trigger the formation of electrical impulses.

The following points provide information that will help you guide the discussion.

  • The cochlea is the hearing (as opposed to balance) part of the inner ear.
  • When the bones of the middle ear (ossicles) vibrate in response to sound, they generate pressure waves in the fluid inside the cochlea.
  • The organ of Corti, located within the cochlea, houses the hair cells that convert (transduce) sound from vibrational energy into electrical impulses.
  • The base of the cochlea, near the ossicles, is stiff and narrow and responds to high-frequency sounds.
  • The apex of the cochlea, away from the ossicles, is flexible and broad and responds to lower-frequency sounds.
  1. To ensure that students understand how sound is represented at various points along the hearing pathway, write the terms “vibration,” “pressure wave,” and “electrical impulse” on the board. Ask students to use the terms to identify the form in which sound energy is represented at each of the eight points pictured.
  • pinna
vibration
  • ear canal
vibration
  • eardrum
vibration
  • ossicles
vibration
  • cochlea
pressure wave
  • organ of Corti
pressure wave
  • auditory nerve
electrical impulse
  • brain
electrical impulse
  1. Distribute to each team 1 copy of Master 4.5, Understanding Form and Function. Instruct team members to work together to complete the handouts.

These masters contain tasks related to the hearing pathway and the treatment of hearing loss. Students may find it helpful to refer to the Black Box sequence of the hearing pathway as they answer the questions. In Part 2, if students have difficulty describing how hearing would be affected by the different situations, use probing questions to elicit answers.

Sample answers to tasks on Master 4.5, Understanding Form and Function, follow:

Part 1
Now that you have properly identified the ear’s transducer, write “yes” beside each phrase that correctly describes one of its characteristics. Write “no” beside each phrase that does not.

yes responds to pressure waves in a liquid
no vibrates in response to sound waves
yes converts vibrational energy to electrical energy
no increases the force of vibrations inside the ear
yes generates nervous impulses
yes is located in the cochlea

Part 2
Use your understanding of the hearing pathway to predict the effect each of the following would have on hearing. Use the choices below for your answers.

For each of the following situations, hearing would

lose loudness fingers blocking the ear canal
lose loudness ruptured eardrum
be lost completely cut the auditory nerve
lose loudness link between the incus and stapes broken
lose loudness buildup of ear wax
gain loudness hand cupped behind the pinna
lose loudness and lose information about pitch damage to hair cells in the cochlea
lose information about pitch and be lost completely (depending on location) damage to part of the brain that processes electrical impulses arriving from the cochlea

Part 3
Identify which statements refer to a hearing aid, which refer to a cochlear implant, or both.

  1. It works as a transducer, converting vibrational energy to electrical (electrochemical and electromechanical) energy. Cochlear implant
  2. It helps people whose hearing loss is caused by problems in the outer or middle ear. Hearing aid
  3. It increases the vibrational energy entering the ear. Hearing aid
  4. It helps sounds bypass injured or absent hair cells. Cochlear implant
  5. It helps people whose hearing loss is caused by problems in the inner ear. Cochlear implant
  6. It can help profoundly deaf people communicate using sound. Cochlear implant
National Science Education Standards icon
Content Standard C:
Disease is a breakdown in structure or function of an organism.
  1. Conclude the activity by reviewing students’ answers to the tasks posed on Master 4.5. During the discussion, supplement the information students have already been given about the hearing pathway as appropriate.

For example, students may be interested to learn that hair cells are unparalleled in their ability to detect the minute levels of vibrational energy in sound waves, and that they respond 1,000 times faster to stimulation than do visual-receptor cells.


Web activity icon Lesson 4 Organizer: Web Version
Activity 1: The Mysterious Black Box
What the Teacher Does Procedure Reference

Introduce the concept of transduction as it relates to human hearing and explain that they will complete a Web-based activity about the hearing pathway.

Steps 1 and 2

Have students log onto Web site and click on “Lesson 4—A Black Box problem: How Do I Hear?”

  • Instruct students to follow the directions and place the images of the hearing pathway in their proper sequence.
Web activity iconStep 3
Activity 2: Understanding Form and Function
What the Teacher Does Procedure Reference
Review the concept of transduction. Step 1

Write the terms “vibration,” “pressure wave,” and “electrical impulse” on the board and have the class apply them to each part of the hearing pathway.

Step 2

Have students complete the tasks on Master 4.5, Understanding Form and Function.

master iconStep 3

Review and discuss student responses to the tasks posed on Master 4.5.

Step 4
Web activity icon= Involves using the Internet.
master icon= Involves copying a master.

print activity icon Lesson 4 Organizer: Print Version
Activity 1: The Mysterious Black Box
What the Teacher Does Procedure Reference

Turn on a lamp and ask how the light bulb produces light.

Step 1

Write “transduction” on the board.

  • Explain that it refers to the process by which energy is converted from one form to another.
  • Ask students if they can name other examples of transducers.
Step 2

Display a transparency of Master 4.1, The Mysterious Black Box.

  • Ask students to identify the question it raises.
transparency iconStep 3

Display a transparency of Master 4.2, A Few Questions.

  • Ask students to answer the questions.
transparency iconStep 4

Explain that students will use Black Box Cards to construct a flow chart of the hearing pathway.

Step 5

Distribute Black Box Cards (from Master 4.3) to each student team and instruct them to put the cards into the correct sequence.

master iconStep 6

Test each team’s card sequence.

  • Have each team explain their sequence.
  • If the sequence is correct ring the bell.
Step 7

Write the names of the hearing-pathway components on the board.

  • Have students match the names with the images on their cards.
Step 8

Construct the hearing pathway on the board.

Step 9
Activity 2: Understanding Form and Function
What the Teacher Does Procedure Reference

Review the concept of transduction.

Step 1
Write the terms “vibration,” “pressure wave,” and “electrical impulse” on the board and have the class apply them to each part of the hearing pathway. Step 2
Have students complete the tasks on Master 4.5, Understanding Form and Function. master iconStep 3
Review and discuss student responses to the tasks posed on Master 4.5. Step 4
transparency icon= Involves using a transparency.
master icon= Involves copying a master.

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