1. Psychology: Chapter 4, Section 3
Hearing
Psychology: Chapter 4, Section 3

2. Sound
When you strum a guitar string, the string bounces back and forth very quickly
These bounces are called vibrations
Sound comes from waves of air pressure resulting from vibrations
The faster the vibrations, the higher the pitch
The taller the vibrations, the louder the pitch
(Note– although both light and sound both travel in waves, they are not related)

3. Wavelengths, Frequency, Amplitude

4. Pitch Sound wave vibrations are very fast– many times per second
The human ear can hear anywhere from 20 to 20,000 cycles per second (20 is a very low sound, 20,000 is a very high pitched sound)
Men have longer vocal cords than women, resulting in longer sound waves, which is why men have deeper voices
Dolphins, dogs, and bats can hear a much wider range of pitch than humans can, and use their hearing more than we do to get around

5. Loudness
The loudness of the sound is determined by the height, or amplitude, of the sound waves
The loudness of a sound is measured in decibels (dB)
Zero dB is the absolute threshold of hearing (the ticking of a watch from 20 feet away)
A soft whisper is rated at about 30 dB
A rock concert is often over 100 dB
Prolonged exposure to 85 dB will cause some hearing loss
Sounds of over 130 dB will cause immediate hearing loss

6. Be Careful with that iPod!

7. The Ear
The ear is shaped to capture sound waves, to vibrate with them, and then to send those messages to the brain
The folds of the outer ear capture whatever sound waves it can, and sends those waves into the ear canal
Inside the canal, the waves hit the eardrum, which vibrates when sound waves hit it (like a drum)

8. The vibrating ear drum then vibrates the three bones in the middle ear: the hammer, the anvil, and the stirrup (the stirrup is the smallest bone in the body)
The vibrations from these three bones stimulate the cochlea in the inner ear (cochlea comes from the Greek word for “snail”)

9. The cochlea is a bony tube that contains fluid and also neurons.
Tiny hairs in the cochlea vibrates from the sound and stimulates the neurons, which then sends the message via the auditory nerve to the processing areas in the temporal lobe of the brain

12. Locating Sounds How do we locate where a sound is coming from?
We can tell where a sound is coming from because we have two ears
The sound is louder in one ear than in the other ear
If a sound is right in front, or above, or directly behind you, it will have the same volume for both ears. So you may tilt your ears a bit to see which direction it’s coming from.
You also may know from context clues which direction a sound is coming from (i.e. a jet engine is probably above you, not below you)

13. A barn owl can locate sounds better than any other creature
Its ears are asymmetrical, with one ear pointed slightly upward and the other downward
Therefore, sounds reach the ears at different times and at different volumes
The owl can perceive the difference between the two signals, and therefore the location and elevation of its prey

14. Owls, dolphins, and bats use echolocation to find their food
Owls, dolphins, and bats use echolocation to find their food. Some humans are able to develop that sense as well.

15. Deafness Not everyone can perceive sound
About one out of 200 people have some significant hearing loss, where they need to be shouted at or need assistive devices
One out of ten have difficulty understanding speech because of their hearing
Deafness may be inherited or caused by disease, injury, or old age

16. Conductive Deafness
If you see a person with a hearing aid, chances are that he or she is suffering from conductive deafness
Conductive deafness is where the sound is not conducted properly all the way to the inner ear
This occurs because of damage to the middle ear
Since the middle ear amplifies sound but isn’t working, the hearing aid can take its place and make sound louder

17. A hearing aid is an electronic device that amplifies sound at different levels for different pitches. Hearing aids consist of a microphone, amplifier and receiver. The come in many styles.

18. Sensorineural Deafness
Many people cannot hear a sound of a certain frequency, or pitch
This is a sign of sensorineural deafness
This is caused by damage to the inner ear
Usually, the neurons in the cochlea are destroyed
There could also be damage to the auditory nerve
This can be caused by prolonged exposure to very loud sounds
If you have left a concert and had a ringing sensation in your ears afterwards, you have destroyed some neurons in your ears

19. Sensorineural Deafness
Sensorineural deafness can be treated with a cochlear implant
The implant is an electronic microphone that stimulates the auditory nerve directly
However, if the damage is to the auditory nerve, a cochlear implant won’t help

20. A cochlear implant turns sound into electrical signals and directly stimulates the auditory nerve, bypassing the damaged hair cells

21. Deafness in the World Today
More people have taken an interest in learning sign language
These people can serve as interpreters for events, sitting in the front of a classroom or a play and signing for those who are deaf
Additionally, more TV shows are “closed captioned,” which puts subtitles on the screen
Scientists are continuing to search for better ways to treat and hopefully cure deafness

22. Videos about Cochlear Implants
How a Cochlear Implant Works by Advanced Bionics
Hearing Cochlear Implants w/ open captions
Scientific American Frontiers Cybersenses

23. Assessment
Complete #1-4 on page 88 from your book in your journal