1. Chapter 6 (D): Hearing

2. Do-Now (Discussion)
Why does one’s voice sound so different when it is recorded and played back?

3. Hearing
Audition:
The sense or act of hearing

4. The Stimulus Input: Sound Waves
Sound waves are compressing and expanding air molecules
Frequency:
The number of complete wavelengths that pass a point in a given time (for example, per second)
Pitch:
A tone’s experienced highness or lowness

5. The Stimulus Input: Sound Waves
Amplitude:
The height of a sound wave
Measures the energy/intensity of the wave
Loudness
Measured in decibels

6. Typical Decibel Levels

7. Loudness of Sound
120dB
70dB

8. The Ear

9. The Cochlea

10. Perceiving Pitch Place Theory: Frequency Theory:
Links the pitch we hear with the place where the cochlea’s membrane is stimulated
Different frequencies vibrate in different places of the cochlea
Problem: low-pitched sounds not localized
Frequency Theory:
The rate of nerve impulses traveling up the auditory nerve matches the frequency of a tone, enabling us to sense its pitch
The entire cochlea is believed to vibrate at a particular frequency
Problem: high-pitched sounds (1,000 waves/second) travel faster than neurons

11. Locating Sounds
Because we have two ears, sounds that reach one ear faster than the other ear cause us to localize the sound.

12. Locating Sounds
Why is it difficult to locate a sound when it occurs directly ahead, behind, overhead, or beneath us?
It is easier to locate a sound when it comes from either side of us; for this reason, to pinpoint a sound, we often need to cock our head, allowing each ear to receive a slightly different message.

13. Hearing Loss and Deaf Culture
Conduction Hearing Loss:
Caused by damage to the mechanical system that conducts sound waves to the cochlea
E.g. punctured eardrum
Sensorineural Hearing Loss:
Caused by damage to the cochlea’s receptor cells or to the auditory nerves
“Nerve Deafness”
Biological changes associated with heredity, aging, and prolonged exposure to ear-splitting noise or music

14. Hearing Loss and Deaf Culture
Cochlear Implant:
A device for converting sounds into electrical signals and stimulating the auditory nerve through electrodes threaded into the cochlea

15. Hearing Loss and Deaf Culture
What are the benefits and limitations of using sign language exclusively in a hearing world?
What should the hearing world’s response be to the use of sign language?

16. Review What is determined by the frequency of a sound? The amplitude?
Discuss the path in which sound travels between entering the ear and reaching the brain.
How do we locate sounds?
What is the difference between Conduction and Sensorineural Hearing Loss?