2. Hearing Our auditory sense

3. We hear sound WAVES

4. Frequency: the number of complete wavelengths that pass through point at a given time. This determines the pitch of a sound or how high or low a sound is.

5. Amplitude or Intensity: is how loud the sound is. The higher the crest of the wave is the louder the sound is. It is measured in decibels.

7. Decibels Every 10 decibels correspond to a tenfold increase in sound. 40 decibels is 100 times louder than 20 decibels. 50 decibels is 1000 times louder than 20 decibels.

9. Sound waves & transduction in the ear Sound waves hit the eardrum, then hammer, anvil, & stirrup. Everything is just vibrating. Then the fluid filled cochlea vibrates. Inside the cochlea is the basilar membrane. On the basilar membrane there are hair cells. When the hair cells vibrate they turn vibrations into neural impulses (organ of Corti). Neural impulse is sent up the auditory nerve, then to thalamus and then to the auditory cortex in the temporal lobe. It is all about the vibrations!!!

11. Pitch Theories Place Theory and Frequency Theory

12. Place Theory Hairs along different places in the cochlea vibrate when there are different pitches. So some hairs vibrate when there are high pitches and others vibrate when there are low pitches. Best explains how we hear high pitches.

13. Frequency Theory All the hairs vibrate but at different speeds (volley principle). The rate of the nerve impulses traveling up the auditory nerve matches the frequency of a tone. Best explains how we hear low pitches.

14. Why do we have two ears?

15. Localization of Sounds Because we have two ears, sounds that reach one ear sooner than the other ear cause us to localize the sound. It’s also louder for one ear.

16. Hearing Deficits Older people tend to hear low frequencies well but suffer hearing loss when listening for high frequencies. http://newt.phys.unsw.edu.au/jw/hearing.html

17. Deafness Conduction Deafness Something goes wrong with the sound and the vibration on the way to the cochlea. You can replace the bones or get a hearing aid to help. Nerve (sensorineural) Deafness The hair cells in the cochlea get damaged. Loud noises (concerts) can cause this type of deafness. NO WAY to replace the hairs. Cochlear implant is possible.