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Chapter 9 Hearing: Physiology and Psychoacoustics


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What is sound?
-waves of dense and less dense air molecules
-created when objects vibrate and pressure changes
What is the speed of sound through air?
340 m/s
What is the speed of sound through water?
1500 m/s
What is amplitude?
perceived as loud or soft
What is frequency?
-how often peaks of sine ways hit our ears
- perceived as high or low pitch
What is our hearing range?
20-20000 Hz
What is loudness measured in?
What are sine waves?
pure pitches
What are complex tones?
sine wave with more than one sinusoidal component of different frequencies
What makes out the outer ear?
pinna, ear canal and concha
What is the tympanic membrane
membrane that vibrates when it hears sound
What are ossicles?
3 bones (malleus, incus, stapes) in the ear that ampliy sound
What are the 2 muscles in the ear?
stapedius and tensor tympani muscle
What is the oval window?
the middle border between middle and inner ear
How do ossicles amplify sound waves?
-work like levers (increase sound by 33%)
-increase energy transmitted
What is the acoustic reflex?
muscles tense when sounds are very loud
When is sound changed into sound waves?
when the oval window pounds against the ear cannal
What is the vestibular system?
contains hair cells, filled with liquid
What is the round window?
relieves pressue in canal when there is a loud sound
What is the cochlea?
Coil structure in temporal lobe
What are stereocilia?
-hairlike on tips on hair cells
-initiate release of neurotransmitters when flexed
What are the inner hair cells?
attached fibers signals to brain
What are outer hair cells?
signals away from brain
What is characteristic frequency?
the frequency to which a particular auditory nerve fiber is most sensitive
What is two-tone suppression?
decrease in firing rate of one auditory nerve due to one tone, when 2nd tone is presented at same time
What is a isointensity curve?
map the plots the firing rate of an auditory nerve fibers against varying frequencies at varing intensities
What is rate saturation?
nerve fiber is firing as rapidly as possible and further stimulation will not increase firing rate
What are low-spontaneous fibers?
auditory nerve fibers with low rates of spontaneous firing (>10 per sec)
What are high-spontaneous fibers?
fibers with high rates of spontaneous firing (>30 per sec)
What are mid-spontaneous fibers?
fibers have medium rates of spontaneous firing (10-30 per sec)
What is temporal code?
tuning of different parts of cochlea to different frequencies
What is phase locking?
firing of neuron at one distinct point in the period of a sound wave at a given frequency
What is the volley principle?
idea the multiple neurons can provide a temporal code for frequency if neurons fires at a distinct point in the period of a sound wave but not every period
Where is the cochlear nucleus?
the first brainstem nucleus that afferent auditory nerve fibers synapse
What is tonotopic organization?
neurons most responsive to low frequency lie on one edge of structures, high-frequency on the other edge
What is conductive hearing loss?
hearing loss caused by middle-ear bones unable to condct sound to inner ear
What is a possible cause of conductive hearing loss?
middle ear filled with mucus from ear infection (otitis media)
What is sensorineural hearing loss?
hearing loss caused by damage to cohlea or auditory nerve
What is senssorineural hearing loss caused be?
-execissive expore to noise
Where is acoustic info processed?
What is the belt area?
respond to more complex characteristics of sound
What is the parabelt area?
-respond to more complex characteristics
-responds to input from other senses

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