1. Hearing 164-170 Our auditory sense

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. The Ear

6. The Path of Sound Outer Ear = collects sound waves Middle Ear = amplifies Inner Ear = Transduction happens

7. Outer Ear Sound wave comes into ear and… Pinna – helps pinpoint location of sound Ear canal → eardrum = tightly stretched – membrane that vibrates when sound hits it

8. Middle Ear The eardrum vibrates and then… – Ossicle bones = hammer, anvil, stirrup amplify vibration – Oval window = another membrane to inner ear

9. Inner Ear Cochlea = fluid-filled, snail shaped tube. Vibrations cause movement in fluid Basilar Membrane – hair cells on floor of cochlea. Bending of them stimulates the auditory nerve cells

10. Transduction in the ear Sound waves hit the eardrum  anvil  hammer  stirrup  oval window. Everything is just vibrating. Then the cochlea vibrates. The cochlea is lined with mucus called basilar membrane. In basilar membrane there are hair cells. When hair cells vibrate they turn vibrations into neural impulses which are called organ of Corti. Sent then to thalamus up auditory nerve. It is all about the vibrations!!!

11. Pitch Theories Place Theory and Frequency Theory

12. Helmholtz’s Place Theory Different hairs vibrate in the cochlea according to different pitches. So some hairs vibrate when they hear high and other vibrate when they hear low pitches.

13. Frequency Theory All the hairs vibrate but at different speeds. But this theory has trouble explaining high pitch sounds because our hairs cannot vibrate at certain speeds.

14. 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 can cause this type of deafness. NO WAY to replace the hairs. Cochlea implant is possible.