1. Perception: Hearing Sound: Amplitude – loudness (decibels)
Wavelength – pitch (frequency – Hertz)
Purity -- timbre

2. Higher frequency wavelengths  higher pitch
Humans can hear 20 Hz  20,000 Hz

3. Ear External Ear = pinna
Vibration of air molecules
Middle Ear – vibration of three small bones (hammer, anvil and stirrup)
Inner Ear – waves in fluid

4. Hearing Process Sound waves follow this path:
Pinna  auditory canal  eardrum  ossicles (hammer, anvil, stirrup)  oval window  cochlea (fluid filled coiled tunnel)  basilar membrane

5. Basilar Membrane
Runs the length of the cochlea and holds hair cells which are stimulated by waves in fluid and convert the physical stimuli into neural impulses

6. Theories of Sound (3)
Place theory – perception of pitch corresponds to vibration of different locations along the basilar membrane

7. Frequency Theory – perception of pitch corresponds to the rate at which entire basilar membrane vibrates

8. Current thought – combination of place and frequency.
Sounds under 1000 Hz use frequency coding, between 1000 and 5000 combination of place and frequency, over 5000 use place coding only

9. Sound Localization
Sound localization is dependent on many things, but especially intensity (loudness) and timing of sounds reaching each ear. The head itself acts as a barrier keeping/slowing some waves from reaching one ear. This results in a difference in intensity to the ears.