How Do We Hear Our World?

Brook Jaentsch

Description of Activity
•	Students learn the basic anatomy and function of each part of the human ear.
•	Students also learn about the cochlea and what frequencies of sound are sensed on the cochlea best. 
•	Students use their knowledge to predict where sounds might be found on the cochlea due to their function in our lives. 
•	The purpose of this activity is to learn the details and purpose of the intricate human ear as well as how it pertains to the music they will be playing on their electric guitar. 
•	This lesson would be appropriate for both a high school anatomy or high school biology class. 

Learning Objectives:

(List measureable objectives)
1.	Students will read about and label parts of the ear.
2.	Students will identify the locations of various types of sounds on the cochlea.
3.	Students will predict and then experiment to find out which types of sounds are more likely or less likely to be heard by the most sensitive parts of the human ear. 
4.	Students will write a conclusion to summarize what they found out about various types of sounds and why these sounds might be absorbed where they are on the cochlea.

Standards:

List The Common Core Math, Next Generation Science Standard and/or SME Competency Gaps. For example:

HS-LS1-2. Develop and use a model to illustrate the hierarchical organization of interacting systems that provide specific functions within multicellular organisms.

HS-LS1-3. Plan and conduct an investigation to provide evidence that feedback mechanisms maintain homeostasis.

Materials Required:

•	Students need a phone with a tuning app installed that can measure frequencies of sound. 

Safety:

safetys:

•	Be sure to measure sounds that are not too loud, or have ear plugs on hand if you are going to measure louder sounds.

References:

https://www.youtube.com/watch?v=0jyxhozq89g
https://www.youtube.com/watch?v=p3Oy4lodZU4
https://www.youtube.com/watch?v=qgdqp-oPb1Q
https://www.youtube.com/watch?v=Ie2j7GpC4JU
http://www.asha.org/public/hearing/Outer-Ear/
http://www.asha.org/public/hearing/Middle-Ear/
http://www.asha.org/public/hearing/Inner-Ear/

 
Activity:

Name _________________________________ Block ____

How Do We Hear Our World?

Background Info:
The Outer Ear: The outer ear consists of the pinna and the ear canal. The pinna – the part of the "ear" that we see on each side of our heads – is made of cartilage and soft tissue so that it keeps a particular shape but is also flexible. The pinna serves as a collector of sound vibrations around us and guides the vibrations into the ear canal. It helps us decide the direction and source of sound.

The Middle Ear: The middle ear begins with the tympanic membrane (ear drum) at the end of the ear canal. The middle ear contains three tiny bones, called the incus, malleus, and stapes. These three bones form a connection from the eardrum to the inner ear. As sound waves hit the eardrum, the eardrum moves back and forth causing these bones to move. As a result, the sound wave is changed to a mechanical vibration.

The Inner Ear: The inner ear contains the sensory organs for hearing and balance. The semicircular canals in the inner ear help control one’s sense of steadiness or balance. These canals are filled with fluids that move as our head moves. 

The cochlea is a bony structure shaped like a snail and filled with two fluids. Inside the cochlea are hair cells that are the nerve receptors for hearing. The movement of the middle ear bones pushes on a membrane (the oval window) in the cochlea. This force moves the cochlea's fluids that, in turn, stimulate tiny hair cells. Individual hair cells respond to specific sound frequencies (pitches) so that, depending on the pitch of the sound, only certain hair cells are stimulated. Signals from these hair cells are then changed into nerve impulses. These nerve impulses are then carried on to the hearing part of the brain.

Watch the following videos on how we hear sounds:
https://www.youtube.com/watch?v=0jyxhozq89g
https://www.youtube.com/watch?v=p3Oy4lodZU4
https://www.youtube.com/watch?v=qgdqp-oPb1Q
https://www.youtube.com/watch?v=Ie2j7GpC4JU

Details about Human Hearing, electric guitars, and the Cochlea:

•	The range of human hearing is generally considered to be 20 Hz to 20,000 Hz, but it is far more sensitive to sounds between 1,000 Hz and 4,000 kHz. 

•	The fundamental frequencies in the playable range of the typical electric guitar covers the range from about 80 Hz to about 1200 Hz. Of course, the harmonics of every note played represent energy at multiples of these frequencies.

•	The most common forms of hearing loss affects the high frequencies. People who suffer from high frequency hearing loss are unable to hear sounds that are in the higher level of frequencies. The stated range for high frequency actually runs from 2,000 Hz all the way through to 8,000 Hz. 

Your Assignment:

For each part of the ear below, locate where that part is in the diagram above and then write the function of the part below:

Stapes: __________________________________________________________________________
Pinna: ___________________________________________________________________________
Tympanic Membrane: _______________________________________________________________
Cochlea: _________________________________________________________________________
Ear Canal: ________________________________________________________________________
Incus: ____________________________________________________________________________
Semicircular Canals: ________________________________________________________________
Malleus: __________________________________________________________________________

Next, label and highlight the Diagram of the Cochlea below with the most sensitive frequencies to the human ear in yellow, the sound frequencies for an electric guitar in pink, and the most common frequencies of hearing loss in blue.  

Finally, label the frequency of 3 sounds that should signal danger, 3 sounds that would be considered soothing, and 3 sounds that are exciting or fun on your cochlea diagram.

Danger sounds: 

-	Sound 1: ______________________________ - Frequency: ___________________ Hz
-	Sound 2: ______________________________ - Frequency: ___________________ Hz
-	Sound 3: ______________________________ - Frequency: ___________________ Hz

Soothing sounds:

-	Sound 1: ______________________________ - Frequency: ___________________ Hz
-	Sound 2: ______________________________ - Frequency: ___________________ Hz
-	Sound 3: ______________________________ - Frequency: ___________________ Hz

Fun or Exciting sounds:

-	Sound 1: ______________________________ - Frequency: ___________________ Hz
-	Sound 2: ______________________________ - Frequency: ___________________ Hz
-	Sound 3: ______________________________ - Frequency: ___________________ Hz

* Download INS Tuner, Pitch Lab, or Optimal Guitar Tuner free on your Iphone and the app will tell you the frequency of each sound. 
Conclusions:

1.	What did you notice about the relative frequency of sounds that were danger sounds? Did they tend to be low, medium, or high frequency sounds?

2.	What did you notice about the relative frequency of sounds that were soothing sounds? Did they tend to be low, medium or high frequency sounds?

3.	What did you notice about the relative frequency of sounds that were Exciting or Fun sounds? Did they tend to be low, medium or high frequency sounds?

4.	Which sounds did you measure that were in the “most sensitive” range for the human ear?

5.	Why do you think our ear is most sensitive to those types of sounds?

Infrasound can cause fear, awe, anxiety, motion sickness, insomnia, and even a temporary supernatural or spiritual feeling in humans. 20 HZ is generally the lowest frequency humans can detect via hearing.  Infrasound can result naturally from severe weather, surf, lee waves, avalanches, earthquakes, volcanoes, bolides, waterfalls, calving of icebergs, auroras, lightening and upper-atmospheric lighting. A tiger’s roar emits infrasound around 19 HZ, inducing fear in its prey.

6.	Human machinery, especially larger machinery or engines emit low frequency infrasound. What type of safety measures should be taken by factories, city planners, even choosing where you want to rent a house?

7.	Mammals like elephants, giraffes, whales and various other animals are much better at hearing infrasound than humans. If you were to compare the Cochlea of humans to these animals, what do you think would be different?

8.	Below is a picture of a human cochlea and an elephant cochlea. 

What do you notice is different?

        					                  Human Cochlea                Elephant Cochlea                          

9.	Why do you think this difference exists?

Answer Key

Quiz:

1.	Write the letter of the graphic below next to the word from the word bank:

Malleus___    Pinna___    Tympanic Membrane___    Incas___    Semicircular Canals___    Stapes___    Cochlea___    Ear Canal

H.

G.

F.

E.

D.

C.

B.

A.

2.	What types of frequencies can generate feelings of anxiety, awe, or insomnia?
a.	Low frequency sounds
b.	Medium frequency sounds
c.	High frequency sounds

3.	What animals can hear infrasound better than humans?
a.	Blue Jays
b.	Fish
c.	Turtles
d.	Elephants

4.	What frequencies of sound are humans most sensitive to?
a.	20 Hz – 500 Hz
b.	500 Hz – 1,000 Hz
c.	1,000 Hz – 4,000 Hz
d.	4,000 Hz – 8,000 Hz
5.	Is the sound from an electric guitar in the range of sounds that humans are most sensitive to?
a.	Yes
b.	No

6.	What is another name for the Tympanic Membrane?
a.	Ear canal
b.	Ear bones
c.	Ear tubes
d.	Ear drum

7.	What is the function of the Semicircular Canals?
a.	Keeping your balance
b.	Hearing high and low pitches
c.	Converting sound to nerve impulses

8.	Do soothing sounds tend to be lower or higher frequency noises?
a.	Lower
b.	Higher

9.	Were soothing sounds found in the range where humans are most sensitive to sound?
a.	Yes
b.	No

10.	Do fun or exciting sounds tent to be lower or higher frequency noises?
a.	Lower
b.	Higher

11.	Were fun or exciting sounds found in the range where humans are most sensitive to sound?
a.	Yes
b.	No

12.	The sound of a thunder storm is:
a.	Low frequency sound
b.	Medium frequency sound
c.	High frequency sound

13.	If an animal has a longer cochlea that curves and spirals more than normal, what would that suggest about the animal’s ability to hear sound?
a.	That animal would be really good at hearing lower frequency sounds.
b.	That animal would be really good at hearing medium frequency sounds.
c.	That animal would be really good at hearing high frequency sounds.

Quiz Key:

a)	Write the letter of the graphic below next to the word from the word bank:

Malleus_B_   Pinna_A_ Tympanic Membrane_G_  Incas_C_  Semicircular Canals_E_  Stapes_D_   Cochlea_H_  Ear Canal_F_

H.

G.

F.

E.

D.

C.

B.

A.

14.	What types of frequencies can generate feelings of anxiety, awe, or insomnia?
a.	Low frequency sounds
b.	Medium frequency sounds
c.	High frequency sounds

15.	What animals can hear infrasound better than humans?
a.	Blue Jays
b.	Fish
c.	Turtles
d.	Elephants

16.	What frequencies of sound are humans most sensitive to?
a.	20 Hz – 500 Hz
b.	500 Hz – 1,000 Hz
c.	1,000 Hz – 4,000 Hz
d.	4,000 Hz – 8,000 Hz

17.	Is the sound from an electric guitar in the range of sounds that humans are most sensitive to?
a.	Yes
b.	No

18.	What is another name for the Tympanic Membrane?
a.	Ear canal
b.	Ear bones
c.	Ear tubes
d.	Ear drum

19.	What is the function of the Semicircular Canals?
a.	Keeping your balance
b.	Hearing high and low pitches
c.	Converting sound to nerve impulses

20.	Do soothing sounds tend to be lower or higher frequency noises?
a.	Lower
b.	Higher

21.	Were soothing sounds found in the range where humans are most sensitive to sound?
a.	Yes
b.	No

22.	Do fun or exciting sounds tent to be lower or higher frequency noises?
a.	Lower
b.	Higher

23.	Were fun or exciting sounds found in the range where humans are most sensitive to sound?
a.	Yes
b.	No

24.	The sound of a thunder storm is:
a.	Low frequency sound
b.	Medium frequency sound
c.	High frequency sound

25.	If an animal has a longer cochlea that curves and spirals more than normal, what would that suggest about the animal’s ability to hear sound?
a)	That animal would be really good at hearing lower frequency sounds.
b)	That animal would be really good at hearing medium frequency sounds.
c)	That animal would be really good at hearing high frequency sounds.

Reviewing Faculty Cohort Members:

•	Lindsey Hansen - NMHS
•	Matt Sniffen - NMHS