2. The Sensation and Perception of Sound
How do we hear?
The Sensation and Perception of Sound

3. Audition (Hearing)
Transduction of sound waves created by vibrations in the air
Sound waves transduced to liquid waves which are transduced to neural impulses

4. Sound Waves: sound travels in distinct waves with 2 physical characteristics
Amplitude (height of wave)
Volume or loudness
Frequency (how often a sound goes through a full cycle)
Pitch

5. Sound Waves and Wave Forms

10. Tips for safe listening
Get headphones that fit
Limit 80 decibel listening to one hour a day
Use smartphone apps to regulate your listening environment
Wear earplugs

11. Hearing Loss (Nerve/Neural)
Sensorineural hearing loss
Hair cells (cilia) have been damaged, usually by loud noise
Most hearing problems
Can be helped with a cochlear implant

12. Conduction Deafness
Problems occur with conduction of sound to the cochlea
Damage to ear canal, eardrum, bones, etc.
Can be helped with a plastic implant or hearing aid

13. Place Theory (Helmholtz)
Pitch Theories
Place Theory (Helmholtz)
Different sound waves trigger activity at different places along cochlea
Brain recognizes the “place” on the membrane where it receives neural impulses
*Bekesy (1957)

14. Frequency Theory
Cochlea vibrates as a whole and triggers neural impulses to the brain at the same rate as sound waves
Brain reads pitch from the frequency of neural impulses

15. Volley Principle
Allows us to process very high frequencies by combining impulses

16. A. Stereophonic Hearing (3D)
Locating Sounds: We use sounds to locate objects especially when seeing is difficult
A. Stereophonic Hearing (3D)
Ears on each side of the head help us locate sounds
The brain uses:
1. Time Disparity: the principle that sound hits each ear at a different time
Brain uses disparities to make precise estimates in locating objects

17. 2. Intensity Disparity:
Principle that sound has a slightly greater intensity in the first ear at which it arrives
Brain uses intensity differences in ears to locate sounds
Which sounds are hardest to locate?
Sounds directly in front or behind us
No timing or intensity differences

19. Join Date: Jul 2005
Location: Raleigh, NC
Posts: 2,700
Umm...let me see here...I'll list these as I'm already a 'borg with the Freedom. Pros Be pretty much on equal terms with the hearing (an ancient goal) Be able to hear and communicate with my children (simply precious to me) Not having to be alert to hear what is said (a big plus!) Hear and communicate out of sight and in dark (love this one) No tinnitus (a nice one) Use of phones...anykind (a very big plus) Can listen all day and not be exhausted (very liberating) Can hear music quite well (wonderful) My speech is surperb now with CI Listening to talk radio again (yea, yea baby!) Cons Battery life could be better (three days...a week would be better) Sometimes I sweat too much and I have to take it off (a pain) Be a little circumspect in sports (gotta watch the head!) Have to wait for even better programming especially for music Dynamic range is limited especially at higher end (I could hear my own whistling before with HA and now it is not so hot and it is tough not being sure if your whistle is right when signaling somebody) Noise can be problematical at times