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Lecture 5

Psychology 2115A/B Lecture Notes - Lecture 5: Eardrum, Oval Window, Sound

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Lecture 5 10/1/2012 11:31:00 AM
What is a stimulus that causes us to hear?
Movement of air molecules caused by vibration
Example the vibration fork (compressing air molecules)
o Molecules go from high pressure/low pressure/high pressure
A sound wave is the patter in the air ( high pressure to low
pressure) refer to diagram
Waves travel faster in water, but they don’t travel as far
Sound waves
o How many times do they repeat themselves in a second
o Measure in cycles per second (CPS) or HERTZ
o Things that you can here have to be AT LEAST 20 times per
second and go up from there
o How much “oomph” was put into the sound
o The strength put into the wave
o If you want something that has the same frequency but
different amplitude : refer to diagram
o The BEL scale: measure the oomph that goes into the sound
It is a log scale
o Associate to sound intensity is the decibel
o Characterizes the relationship between sound waves
o Have equivalent amplitude and frequency but one could be
leading the other
o Measured in degrees ( 360 degrees- the time between the
two peeks)
The sense organ
the sense receptor for audition is the ear

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the thing that you see is the outer ear PINNA
o acts as an antenna (grabs the sound waves from the
the goes through the auditory canal
o what’s picked up from the environment then goes through the
o increases pressure so we don’t loose the sound
ear drum- the tympanic membrane
o will vibrate from the pressure coming form the canal
o the ear drum is in the middle ear ( begins it)
o the three bones in the ear- the malleus the incus and the
stapes all vibrate
o the vibration goes from the bones to the oval window
the osicles
o don’t respond to low frequency’s (like your heart beating)
o they respond to the vibration off your jaw ( that’s why when
you hear your own voice recorded you sound different
the oval window
o entering the inner ear, the stapes hit the fluid inside making
the vibration (mechanical stimulus)
o moves the basilar membrane
o three canals
the vestibular canal
the cochlear duct
most important
separated by the basilar membrane
the organ of corti (hard plate) is sitting on top of
it this moves as a result of the hairs underneath
it moving (caused by the mechanical stimulus of
the basilar membrane)
hairs are attached to the top and the bottom of
the organ of corti
the tympanic canal
o the round window
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