ch 11: Hearing

Question 1

How can sound be described physically and perceptually?

Answer 1

physically: pressure waves in air via vibrating object
perceptually: pattern of kinetic energy in eardrum

Question 2

What makes up the timbre of a sound?

Answer 2

-character/nature of sound
-ex violin vs piano
-due to diff frequency components (fundamental freq and harmonics)
-sine wave, square wave, sawtooth wave

Question 3

What does the equal loudness curve represent?

Answer 3

-sound levels that create equal perception of loudness at diff frequencies

Question 4

What are the receptors for audition, and how does transduction take place?

Answer 4

-vibes - eardrum vibes - ossicles vibe - oval window vibes - basilar membrane vibes…
-organ of corti goes up and down
-tectorial membrane goes back and forth
-….stereocilia to bend via fluid flow (causing electric signals)
-steriocilia of hair cells bend in one direction = tip links to stretch, opening channel trap door = K+ flow into cell = electrical signal
(bend in other direction = trap door closes = no electrical signal
-back and forth hair bending = alternating bursts of electrical signals …
-NT release at the synapse between inner hair cells and auditory nerve fibres = transduction!!!
-these electrical signals can synchronize w pressure changes of pure tone (phase locking)
…pressure increase = bend to the right = fire
-pressure decrease = bend to left = no fire

Question 5

What are the pathways for audition?

Answer 5

synapse in subcortical structures:
1. cochlear nucleus
2. superior olive nucleus
3. inferior colliculus
4. medial geniculate nucleus
reaches the primary auditory cortex:
-TEMPORAL LOBE

Question 6

How do place, frequency, traveling wave, and volley theories explain pitch perception?

Answer 6

-see paper and class notes

Question 7

What are the symptoms of and treatments for tinnitus?

Answer 7

symptoms of tinnitus:
-ringing or experience sound when no sound
-can’t concentrate, anxiety, depression
theories of cause:
-destroy hair cells = brain remaps = abnormal brain activity
-decreaase in incoming stimulation = less inhibition = more excitation and phantom sound
treatments:
-no cure, white noise helps cancel out the ringing

Question 8

phase

Answer 8

point along wave measured in degrees

Question 9

amplitude

Answer 9

-displacement of wave from peak to trough
-how high the wave goes
-associated w/loudness
-logarithmic, decibels

Question 10

frequency

Answer 10

-# of sound wave cycles per second
-how fast the wave waves
-Hz (1Hz = I cycle per second)
-associated w/pitch

Question 11

pitch

Answer 11

-Hz
-associated w/frequency
-low to high sounds
-affected by intensity: high pitch seem higher w/ increased intensity

Question 12

Loudness

Answer 12

-associated w/amplitude
-dB / stone

Question 13

Octave

Answer 13

-note is one octave about another when its frequency is double of the note its being compared to

Question 14

-components of frequency…
-diffs in these affect…

Answer 14

1. fundamental: lowest frequency in a Fourier spectrum of complex sound wave. repetition rate of a complex tone
2. harmonic: components of complex sound having frequencies that are multiples of the fundamental

-timbre

Question 15

pure tone vs complex tone

Answer 15

pure: only one frequency
complex: multiple repeating frequencies. multiple pure tones added tether

Question 16

first harmonic

Answer 16

-pure tone w/frequency equal to fundamental frequency
-AKA fundamental of tone

Question 17

audibility curve

Answer 17

some frequencies have higher/lower thresholds for for hearing
-threshold for hearing vs frequency
-hear 20-20kHz, best @2-4k

Question 18

effect of missing fundamental

Answer 18

-pitch stays the same even with fundamental or other harmonics removed

Question 19

auditory response area

Answer 19

what we can hear (from threshold to pain) of diff frequencies

Question 20

auditory adaptation

Answer 20

-same sound seems softer when presented for long time
-get used to it = sounds quieter

Question 21

auditory fatigue

Answer 21

-temporary hearing loss b/c high intensity sounds
-frequencies above the sound are lost

Question 22

structure and function of outer ear

Answer 22

-pinnae
-auditory canal protects tympanic membrane (eardrum)
-canal can enhance some sounds via resonance

Question 23

structure and function of middle ear

Answer 23

-on other side of tympanic membrane
-3 ossicles that concentrate the vibes b/c inner = water so need to make the vibes strong
-melleus, incus, stapes
-stapes knocks on oval window (vibes it)
-Eustachian tube equalizes pressure from middle ear w/outside

Question 24

structure and function of inner ear

Answer 24

-cochlea
-scala vestibuli + scala tympani
-separated via cochlear partition (scala media)
-inside cochlear partition = organ of corti (hairy), (basilar membrane and tectorial membrane are what forms the cochlear partition)
-tips of the hair cells have stereo cilia = bend in response to pressure changes (sound waves)

-basilar membrane sorts tones by frequency - high frequency = vibe closer to the beginning (base, near oval window)
-low frequency = fire closer to the end of the snail (apex)
-tonotopic map = map of diff vibes along basilar membrane based on frequency

Question 25

resonance

Answer 25

-auditory canal enhance sounds
-sound waves that reflect back interact w/ones going in to amplify
-resonant frequency = the most reinforced frequency

Question 26

neural frequency tuning curve

Answer 26

-neural fire of a neutron based on certain frequency
-characteristic frequency = frequency the neutron fires most to

Question 27

Audition once it reaches the cortex
tonotopic organization

Answer 27

-neurons respond to certain frequencies found close tgthr
-primary auditory cortex in temporal lobe
-neurons activated by similar frequencies are close tgthr
-complex sounds can be broken down into their simple waves via auditory cortex
-thus, not necessary to have one neutron per each sound
-instead, pattern of multiple neutrons firing = perception of sound (population coding, not sparse coding)
-however there are some neutrons sensitive to certain one stimuli, ex monkeys

Question 28

What are some effects of noise, and how can hearing loss be prevented?

Answer 28

1. presbycusis
   -over time hair cell damage
2. noise-induced hearing loss
   -degeneration of hair cells b/c loud and damage to organ of corti
3. hidden hearing loss
   normal hearing but trouble w/noise environments
   -maybe b/c permanent damage to auditory nerve fibres caused by loudness, while hair cells have recovered