1. Hearing
The Nature of Sound

2. AP Standards for Sensation and Perception
Discuss basic principles of sensory transduction, including absolute threshold, difference threshold, signal detection, and sensory adaptation.
Describe sensory processes (e.g., hearing, vision, touch, taste, smell, vestibular, kinesthesis, pain), including the specific nature of energy transduction, relevant anatomical structures, and specialized pathways in the brain for each of the senses.
Explain common sensory disorders (e.g., visual and hearing impairments).
Describe general principles of organizing and integrating sensation to promote stable awareness of the external world (e.g., Gestalt principles, depth perception).
Discuss how experience and culture can influence perceptual processes (e.g., perceptual set, context effects).
Explain the role of top-down processing in producing vulnerability to illusion.
Discuss the role of attention in behavior.
Challenge common beliefs in parapsychological phenomena.
Identify the major historical figures in sensation and perception (e.g., Gustav Fechner, David Hubel, Ernst Weber, Torsten Wiesel).

3. Activity
In your rows, decide the placement of each noise by decibel category.
You have 5-6 minutes to complete this activity once you have been given your group’s sheet.
We will check out answers in just a minute.
Answers to Audio Quiz

4. Auditory System The Ear Outer ear Middle ear Inner ear
Pinna & external auditory canal
Middle ear
Eardrum (tympanic membrane), hammer, anvil & stirrup
Inner ear
Oval window, cochlea (basilar membrane inside)
The hammer, anvil, and stirrup are the three smallest bones in the human body.
Sound waves are collected in the outer ear, beginning with the fleshy pinna. Some animals, such as dogs, cats, and deer, can wiggle this structure like a radar dish to maximize the reception of sound (humans cannot). Research shows that the folds of the pinna enable people to pinpoint the location of sounds – for example, whether they come from above us or below, in front or behind.
The sound waves are then funneled through the auditory canal to the eardrum, a tightly stretched membrane that separates the outer and middle portions of the ear.
The eardrum vibrates back and forth to the waves, thereby setting into motion a series of tiny connect bones in the middle ear – the hammer, the anvil, and the stirrup (which happen to be the smallest bones in the body). This middle-ear activity amplifies sound by a factor of thirty. The last of these bones, the stirrup, then vibrates against a soft inner-ear membrane called the oval window.
This vibration is transmitted to the fluid that fills the canals of the cochlea, a snail-shaped tube – and the resulting motion presses up against the basilar membrane, which brushes up against an array of 16,000 sensitive hair cells. These hair cells bend, exciting fibers in the auditory nerve – a bundle of axons that link to the auditory centers of the brain.

5. The Outer Ear

6. Auditory System - Hearing
The process of hearing
Air waves move the tympanic membrane (eardrum), which moves the hammer, anvil and stirrup. These amplify the air waves and pass them on . . .
to the basilar membrane in the cochlea.
Here, different frequencies are transduced (converted) by hair cells (i.e., the receptor cells of the ear) into nerve impulses that the auditory nerve sends to the auditory cortex of the brain to identify sounds.

7. The Inner Ear

8. The Middle Ear

9. How does hearing work? Click on the picture below to watch a video illustrating the hearing process.

10. Types of Hearing Impairments: Conductive Hearing Loss
Conductive hearing loss refers to problems with the mechanics of the outer or middle ear. It prevents vibrations from passing from the eardrum to the cochlea. It can be caused by a ruptured eardrum or an infection.
Conductive loss can be temporary. Eardrums can sometimes repair themselves, or an infection can clear up and not leave permanent damage.
If the damage is permanent, it can be treated with a hearing aide that amplifies sound.

11. Types of Hearing Impairments: Sensorineural Hearing Loss
Sensorineural (nerve) hearing loss refers to problems that have caused nerve damage in the inner ear or auditory pathway.
Normal aging causes loss of hair cells in the cochlea, and exposure to loud noises can cause irreparable damage to the cells, too.
This type of hearing loss can only be “repaired” with a cochlear implant (see p. 116). An ordinary hearing aide doesn’t help.

13. two theories of how the brain hears pitch
Place theory
Frequency theory
Hermann von Helmholtz, 1863
The pitch a person hears depends on where the hair cells that are stimulated are located on the organ of Corti.
This works best for moderate to high pitches of above 1000 Hz, which vibrate the basilar membrane unevenly.
Ernest Rutherford, 1886
The pitch is related to how fast the basilar membrane vibrates. The faster it vibrates, the lower the pitch.
This works best only up to 1000 Hz.

14. So What is Pitch? Pitch refers to how high or low a sound is.
Is place theory or frequency theory correct? The answer is BOTH.
___________________________________________________________________
A final theory is the VOLLEY PRINCIPLE, which accounts for pitches from 400 Hz up to about 4000 Hz. The neurons take turn firing (volleying) and send three 1000 Hz messages for a 3000 Hz pitch.

15. Your Own Hearing
Use the 60/60 rule: no more than 60% volume for no more than 60 minutes at a time.
If you are using earbuds and the people around you can hear your music, you could be causing permanent hearing loss, especially if they are hearing it from across the room.
Head phones do less damage than earbuds because they aren’t placed inside the ear canal.
For more information on the ear, visit for a teen-friendly article.

16. AP Standards for Sensation and Perception
Discuss basic principles of sensory transduction, including absolute threshold, difference threshold, signal detection, and sensory adaptation.
Describe sensory processes (e.g., hearing, vision, touch, taste, smell, vestibular, kinesthesis, pain), including the specific nature of energy transduction, relevant anatomical structures, and specialized pathways in the brain for each of the senses.
Explain common sensory disorders (e.g., visual and hearing impairments).
Describe general principles of organizing and integrating sensation to promote stable awareness of the external world (e.g., Gestalt principles, depth perception).
Discuss how experience and culture can influence perceptual processes (e.g., perceptual set, context effects).
Explain the role of top-down processing in producing vulnerability to illusion.
Discuss the role of attention in behavior.
Challenge common beliefs in parapsychological phenomena.
Identify the major historical figures in sensation and perception (e.g., Gustav Fechner, David Hubel, Ernst Weber, Torsten Wiesel).