EAR JOURNEY

FIRST...

• Sound waves travel through air
• Waves are captured by the outer ear (pinna)
• Travel through auditory canal to the ear drum

• A tight membrane
• Vibrates when waves are detected

NEXT...

• The middle ear tranmits the vibration
• Hammer, anvil, and stirrup receive vibrations(ossicles)
• Vibrations then travel through the oval window and to the cochlea

• Snail shaped
• Fluid filled inner ear structure
• Where receptor cells are located
• Sloshing of fluid and and pressure changes triggers basilar membrane

THEN...

• Hair cells in basilar membrane bend
• Hair movement triggers impulse at base of nerve cells
• These small hairs are often referred to as "cilia"
• Auditory nerve takes over and sends impulse to brain

• Nerve cell fibers' axons make up auditory nerve
• Sends neural messages to temporal lobes auditory cortex (via thalamus)
• Auditory Cortex- place in brain where hearing is processed

*TRANSDUCTION*

• When sound waves are converted neural impulses our brain can understand
• Physical energy becomes electrical signals

*WAVE PROPERTIES*

• Amplitude= volume/ sound intensity
• Wavelength= pitch

*PERCEPTION *

• Volume- soft tunes activate a few hairs, loud tunes activate many hairs
• Theories: place theory, volley principle, and frequency theory
• Pitch- sounds corresponding primarily to frequency of sound of vibrations

*PLACE THEORY*

• We hear different pitches
• Sound waves trigger different activity at different places in basilar membrane
• Brain determines pitch by recognizing specific place generating neural signal
• Pitch depends on position
• Deals with high pitch

*VOLLEY PRINCIPLE*

• Derived from frequemcy theory
• High frequency sounds are experienced too frequently for a neuron to adequately process and fire
• Neuron acrtion potentials combine the multiple stimuli into a "volley" in order to process the sounds.
• When combined, a greater frquency can be encoded

*FREQUENCY THEORY*

• Brain reads pitch by monitoring frequency
• Pitch is determined by how fast neural signals to the brain
• Different frequencies make the basilar membrane vibrate at different rates
• Can cause neural impulses to be sent at different rates
• Deals with low pitch

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