task 6 Flashcards
(28 cards)
sound wave
the pattern of air pressure changes
when the diaphragm of the speaker:
->moves outwards - compression of air molecules
->moves inwards- refraction of air molecules
by repeating this process 100 of times in a second, the speaker creates a pattern of alternating gif and low pressure region in the air, which travels at about 340 m/s.
pure tone
a type of sound wave that occurs when changes in air pressure create a pattern like the function sin
effect pf the missing fundamental
if a harmonic of a complex tone is removed, the tone’s pitch stays the same
not the same for tone’s timbre
if a harmonic of a complex tone is removed, the tone’s timbre DOES change
attack and decay
timbre also depends on a tone’s attack (build up) and decay (last 0, 5 seconds)
resonance
occurs in the auditory canal when sound waves that are reflected back from the closed end of the auditory canal interact with sound waves that are just entering
amplifying for 1000-5000 HZ
the amplifying effect works for frequencies between 1000 and 5000 Hz (most sensitive for hearing)
cochlear amplified
mechanical process that takes place in the outer hair cells - explains the narrow running curve
-> amplifying the vibration of the basilar membrane-> sharpness the running curve
the place theory
a pure tone’s frequency activates specific neurons in one place on the basilar membrane-> the brain determines the pitch by looking at which neurons are responding
the effect of missing fundamental contradicts this theory
resolved and unresolved harmonics
*resolved harmonics- lower harmonics, narrow excitation curve
*unresolved harmonics= higher harmonics, smooth excitation curve
difference lies in how well the cochlea can distinguish frequencies — lower harmonics are resolved well (sharp peaks), while higher harmonics blend together (smooth curve).
also
*resolved harmonics- good pitch perception
*unresolved harmonics- bad pitch perception
amplitude- modulated noise
stimulus that wasn’t associated with a particular presence on the basilar membrane
-> pitch can be perceived without place information
Key Takeaway: The brain can perceive pitch even if the cochlea doesn’t have a specific location that resonates with that pitch.
temporal coding
the timing of firing groups of neurons provide information about the fundamental frequency of a complex tone-> information about the pitch
phase locking is linked to pitch perception
* Key Point: The neurons don’t fire at every cycle but always at the same phase point (e.g., the peak).
Why It Matters: Helps explain how we perceive pitch even when place coding is not clear.
Example: For a 300 Hz tone, neurons fire 300 times per second, but not necessarily all at once (they can fire in groups).
volley principle
multiple neurons can provide a temporal code for frequency -> temporal coding + population coding
pitch neurons
respond to stimuli associated with a specific frequency - a specific pitch
found in the primary auditory cortex
pitch neurons location
the most pitch neurons can be found in the anterior auditory cortex
this region is responsible for resolved harmonics
outer hair cells damage
basilar membrane has only broad responses-> harder to separate sounds
inner hair cells damage
loss of sensitivity ->dead region of cochlea
prebycusis
age related hearing loss due to damage to inner hair cells over time->loss of sensitivity and affects primarily high-frequencies
hair cell damage results from noise exposure, substance abuse, age degeneration
greater loss of sensitivity at higher frequencies
noise induced hearing loss
exposed to loud noises damages the hair cells-> degeneration of the cochlea (using ear protection and reducing volume levels are crucial)
observed damage to the organ of corti and inner hair cells
leisure noise
ex: riding a motorcycle, loud music
hidden learning loss
damaged auditory fibers-> problems in hearing speech in noisy environments
individuals that may have normal results at a standard hearing test but struggle to understand speech, especially in noise environments, due to damage to auditory nerve fibers.
place code
different places on the cochlea and in the auditory system are sensitive to different sound frequencies
so the brain receives spatial information
timing code
different frequencies are signaled by the timing of neural responses in auditory nerves
*limitation: there is a refractory period during which neurons can’t generate an action potential
frequency and responses are not coded by one single auditory nerve fibre but by a group of fibre based on the cochlear partition
auditory nerve fibres
the frequency selectivity of the fibers decreases as the sound intensity/ amplitude increases
2 tone-suppression
presence of a second tone with different frequency reduces the firing rate if an auditory nerve fiber that responds to a first tine
- it works more when the second tone has lower frequency than the first tone because it causes vibration along most of the basilar membrane.
