hearing 164-170 our auditory sense. frequency the number of complete wavelengths that pass through...
TRANSCRIPT
Hearing 164-170
Our auditory sense
Frequency the number of complete wavelengths that pass through point at a
given time. This determines the pitch of a sound.
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.
The Ear
The Path of Sound
• Outer Ear = collects sound waves• Middle Ear = amplifies• Inner Ear = Transduction happens
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
Middle Ear
• The eardrum vibrates and then…– Ossicle bones = hammer,
anvil, stirrup amplify vibration
– Oval window = another membrane to inner ear
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
Transduction in the ear• Sound waves hit the eardrum anvil
hammerstirrupoval 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!!!
Pitch Theories
Place Theory and Frequency Theory
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.
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.
DeafnessConduction 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.