1. Hearing Aka: Audition

2. Frequency the number of complete wavelengths that pass through point at a given time. This determines the pitch of a sound.

3. Amplitude is how loud the sound is. The higher the crest of the wave is the louder the sound is. It is measured in decibels.

5. Do You Hear What I Hear? The outer ear funnels sound waves to the eardrum. The bones or ossicles (Hammer {malleus}, Anvil {incus} & Stirrups {stapes}) of the middle ear amplify & relay the eardrum’s vibrations through to the inner ear, the oval window of the fluid-filled cochlea. The resulting pressure changes in the cochlear fluid cause the basilar membrane to ripple, bending the hair cells on the surface (16,000). Hair cell movements trigger impulses at the base of the nerve cells, whose fibers converge to form the auditory nerve, which sends neural messages to the thalamus & on the auditory cortex.

7. The middle ear transmits the eardrum’s vibrations through a “piston” made of 3 small bones (the hammer, anvil and stirrup) to the cochlea (snail shaped tube). The incoming vibrations cause the cochlea’s membrane (oval window) to vibrate, moving the fluid that fills the tube. This motion causes ripples in the basilar membrane (hair cells). The movement of cells triggers impulses in the adjacent nerve fibers which form the auditory nerve that connects via the thalamus to the temporal lobe. The Process of Hearing

8. See pages 126-127

9. How do we detect loudness? NOT from intensity of hair cell’s response A soft, pure tone activates only the few cells attuned to its frequency Given louder sounds its neighbor hair cells also respond…the brain interprets loudness from the NUMBER of activated hair cells!

10. Why does our own voice sound unfamiliar when we hear it on a recording? When we speak, we hear both the sound conducted by air waves to the outer ear & that carried directly to auditory never by bone conduction. –click your teeth, or munch a crunch *The strictly air-conducted sound that others normally hear (when we hear our voices on tape) is thinner. You can hear the sound waves conducted by bone if you plug your ears & talk in a normal voice.

11. How do we perceive differences in pitch? There are two theories……..

12. Helmholtz’s Place Theory We hear different pitches because different sound waves trigger activity at different places along the cochlea’s basilar membrane.

13. Frequency Theory We sense pitch by the basilar membrane vibrating at the same rate as the sound. But this theory has trouble explaining high pitch sounds because our hairs cannot vibrate at certain speeds. This problem can be explained using the volley principle. http://channel.nationalgeographic.com/brai n-games/videos/high-frequency-hearing- test/http://channel.nationalgeographic.com/brai n-games/videos/high-frequency-hearing- test/

14. Why do we have two ears?

15. How We Locate Sounds

16. Hearing loss Conduction Hearing Loss: caused by damage to mechanical system of ear. Sensorinueral hearing loss: caused by damage to cochlea’s receptor cells or to auditory nerves.

17. Cochlear Implant Cochlear Implant:device converting sounds into electrical signals & stimulating the auditory nerve through electrodes threaded into the cochlea.

18. Hearing Loss Damage to hair cells account for most hearing loss. (i.e.:carpet fibers…) “Earplugs or walk away.” –After exposure to loud noise, when your ears ring, ears are alerting us to possible hearing damage

19. The question “If a tree falls in the forest and there is no one around to hear it, does it still make a sound?” can now be answered. No, it would make no sound. –Sound is a purely psychological sensation that requires an ear (and the rest of the auditory system) to produce it. If a tree falls in the forest…