Section 5 Flashcards
How does sound come about?
From pressure fluctuations in the air
What determines the loudness of sound?
The amplitude of the sine waves that represent the air fluctuations
What is loudness?
The psychological aspect of sound related to perceived intensity or amplitude
How is amplitude measured?
Decibels
What does dB = 0 mean?
The pressure fluctuation corresponds to the minimal auditory sound for most people
TRUE/FALSE
dBs are more reflective of subjectively perceived sound than actual sound pressure
true
How does dB if sound pressure increases by x10?
Increases by +20
What is intensity of sound?
Corresponds to the energy of the sound wave when it hits a 2D surface, such as the eardrum
What is pitch?
The psychological aspect of sound related mainly to the fundamental frequency
What do we call sounds that only have one frequency?
Pure tones
Sounds that have a lower frequency have a _______ (lower/higher) pitch
lower
What is a spectrum of sound?
It’s an easy way of breaking down complex sounds using bars whose height represents the amplitude and the position on the X axis represents which frequency that sound is at
What is a harmonic spectrum?
The spectrum of a complex sound in which the energy is integer multiples of the fundamental frequency
What is a fundamental frequency?
The lowest-frequency component of a complex periodic sound
What does it mean if different spectra of complex sounds have the same fundamental frequency?
They will all have the same pitch
If several complex sounds have the same pitch, does that guarantee they will have the same loudness?
No, loudness will depend on the amplitude differences
What is timbre?
The psychological sensation by which a listener can determine that two sounds with the same loudness and pitch are dissimilar
If two sounds have different timbres, what does that tell us about their harmonic spectrum?
Their spectra are different
What is a missing-fundamental effect?
The fundamental frequency is missing in the harmonic spectrum, but the pitch listeners hear still corresponds to that fundamental frequency
How can we hear the fundamental frequency even if it is absent in the spectrum?
The superposition of the different harmonics will recreate a peak that has the frequency of the missing fundamental
Describe audibility of a sound
The combination of frequency and amplitude
What is an equal-loudness curve?
A graph plotting sound pressure level (dB) against the frequency for which a listener perceives constant loudness
List the three sections that make up the ear
Outer, middle, and inner
What structures make up the outer ear?
Auditory canal and pinna
What structure borders the outer and middle ear?
Tympanic membrane
What structure is at the border of the middle and inner ear?
Oval window
What are the three bones that transduce the sound signal to the oval window?
Malleus, incus and stapes
which ear structure amplifies sound signals?
The ossicles
There are two muscles part of the middle ear - what are they?
Tympani muscle and stapedius muscle
What is the role of the tympani and stapedius muscles?
Protect the ear from the sound being too loud by stopping the tympanic membrane and ossicles from vibrating
What two main structures make up the inner ear?
Vestibular organs and cochlea
What are the vestibular organs important for?
Sense of equilibrium
What is the cochlea important for?
Hearing
Inside the cochlea there is a fluid that is distributed across three main canals - list them
vestibular canal, middle canal, and tympanic canal
What two membranes separate the three canals?
Tectorial membrane and basilar membrane
Where is the organ of corti located? what does it do?
It is located on the basilar membrane and contains nerve cells that are responsible for hearing
What do we call the nerve cells located on the organ of corti?
Hair cells
How many hair cells are there?
4 in total - 1 inner and 3 outer
What do you call the tiny hairs on top of each hair cell?
Stereocilia
What part of the hair cells are attached to the tectorial membrane?
Stereocilia
What causes the basilar membrane to move up and down?
Movement of cochlear fluid
How does a change in air pressure transduce into an electrical signal?
The stereocilia on the hair cells have tip links that connect the stereocilia, and when they move back and forth it opens the link which allows K+ to enter the hair cell, causing the cell to depolarize and release neurotransmitter
What are the two main ways the auditory system can differentiate between different frequencies?
- Cochlear place code
2. Temporal encoding of frequency
Describe the structure of the basilar membrane
As the membrane extends from the base of the cochlea, it becomes wider and thinner, making the tip of the membrane more sensitive to lower frequencies and the base being more sensitive to higher frequencies
What is the cochlear place code?
The theory that because the sensitivity of the basilar membrane works via a gradient, specific frequencies will be related to movement of specific parts of the membrane
What is the role of characteristic frequency in the cochlear place code?
Auditory nerve fibers are selective for a given frequency, and these different fibers will be connected to different hair cells located at different points along the basilar membrane that corresponds to which frequency they are selective for
What are threshold tuning curves?
Describes the characteristic frequency for a specific auditory nerve neuron
Auditory nerve firing is phase-locked, meaning these neurons systematically fire at a given time point. When exactly will these neurons fire?
When the amplitude starts increasing because the liquid in the cochlea move upward which tilts the stereocilia and causes the hair cells to fire
What is the volley principle?
When the frequency is high the refractory period of the fibers does not allow the neurons to fire fast enough, but even if individual neurons cannot keep the pace, the whole population of neurons can still temporally encode the frequency
Which three nuclei in the brainstem will the auditory nerve from both ears project onto?
cochlear nucleus, superior olive, and inferior colliculus
The auditory nerve projects to the _______ (ipsilateral/contralateral) cochlear nucleus, but from the cochlear nucleus the information is sent to the ______ (ipsilateral/contralateral) and _______ (ipsilateral/contralateral) superior olive
contralateral, ipsilateral, contralateral
The inferior colliculus receives either ______ (direct/indirect) input from the cochlear nucleus or _______ (direct/indirect) input from the superior olive
direct, indirect
Once the information passes the inferior colliculus, what next brain structure does the information get sent to?
The medial geniculate nucleus in the thalamus
Where does the information travel after reaching the thalamus?
The auditory cortex
Where is the auditory cortex located? More specifically, where is the primary auditory cortex located?
Temporal lobe
lateral fissure
What structures surround the primary auditory cortex?
Belt and parabelt
TRUE/FALSE
the belt and parabelt does not respond to pure tones
true
Describe the tonotopic organization in the primary auditory pathway
Neurons that respond to different frequencies are organized anatomically in order of frequency
Where does tonotopic organization begin?
in the cochlea
List two causes of hearing loss
- loss of sound conduction to the cochlea (conductive hearing impairment)
- damage to the cochlea (sensorineural hearing impairment)
How do cochlear implants work?
bypasses the damaged cochlea by installing electrodes which will be able to simulate the neural patterns of activity that would normally be associated with a typically functioning cochlea
What is tinnitus?
The perception of a sound in the absence of sound waves
Describe the leading hypothesis for the cause of tinnitus
following hearing loss, the brainstem increases the gain in the auditory pathway to compensate, which also amplifies neural noise
What ear structures would likely lower their threshold and result in tinnitus?
Cochlear nucleus, inferior colliculus, and auditory cortex
What is an azimuth?
the angle of a sound wave relative to the center of the head
What is the interaural time difference (ITD)?
The difference in time between a sound arriving at one ear vs the other
Where are coincidence detector neurons located?
In the superior olive
Explain how a coincidence detector neuron works
When a sound enters one ear it will travel to the contralateral superior olive. The sound will eventually reach the other each and that will also send a signal to the ipsilateral superior olive. When the two nerve impulses meet at a coincidence detector neuron it will cause that specific neuron to discharge which will encode the ITD for the sound delay
What is the interaural level difference (ILD)?
The difference in the level between a sound at one ear vs the other
What angle(s) is the ILD largest? Which angles is there no associated ILD?
(+/-) 90 degrees has the largest ILD, whereas 0 and 180 degrees has no ILD
How does frequency affect ILD?
Higher frequencies have more ILD dependence because the sound is easier to block when traveling in space, but as you go to lower frequencies the ILD disappears because the sound waves are not being blocked anymore
The superior olive receives _______ (excitatory/inhibitory) input from the ipsilateral ear, and _______ (excitatory/inhibitory) input from the contralateral ear
excitatory, inhibitory
What is a limitation of ITDs and ILDs?
They cannot tell us how far away an object is on a given azimuth
Define the inverse square law
The intensity of a sound decreases as a function of the inverse of the square of the distance
Why does the intensity of higher frequencies decrease as a function of distance more rapidly than intensities coming from shorter frequencies?
The further the sound is the more obstacles it will encounter before reaching your ear, and shorter frequencies are more resistant to these obstacles so they are less affected
Describe the change in spectral composition of sound as a function of distance
Sounds coming from a further distance tend to be composed of lower frequencies, whereas sounds that are closer to you are generally composed of higher frequencies
What is a cone of confusion?
A cone-shaped set of points where a sound source produces identical phase delays and transient disparities
What is a directional transfer function (DTF)?
A measure that describes how the pinna, ear canal, head, and torso change the intensity of sounds with different frequencies that arrive at each ear from different locations in space
Is a DTF constant?
No, it is constantly adapting as you grow up or after you damage one of your key structures responsible for it
What is auditory stream segregation?
The perceptual organization of a complex acoustic signal into separate auditory events for which each stream is heard as a separate event
List 7 acoustic cues that can be used to segment audition
- location of sounds
- frequency (pitch) of sounds
- timing of sounds
- timbre of sounds
- onset of sounds
- rule of good continuation
- higher-order information (restoration effects)
Describe grouping by frequency
Tones that have similar frequencies will tend to be grouped together
Describe grouping by time
Tones that are close together in time will tend to be grouped together
How is grouping by time influenced by grouping by frequency?
They are generally independent from one another, however sometimes they will complement each other and other times they may compete
How are you most likely to group two sounds if their timing difference is very small vs very large?
If the difference in timing is very small grouping instead by frequency will likely give you the same result, however as the timing difference becomes larger you may start hearing as if there are multiple sources
Describe grouping by timbre
Tones that have similar timbre will tend to be grouped together
Describe grouping by onset
When sounds begin at different times, they appear to be coming from different sound sources
How does the rise time of a set of tones affect how we perceive them?
When a set of tones gradually rise we perceive it as one cluster, however when the rise is abrupt it is easier to identify the different tones as solo events
Describe the continuity effect
Even if there is a gap in the sound, as long as the gap is filled with noise you will still hear the sound as if it were continuous
What happens if there is a sound gap but is not filled with noise?
The sound will be perceived as separate chunks
Describe the restoration effect
In spite of interruptions, one can still hear a sentence if the gaps are filled with noise
Explain why we can still hear a proper sentence even if there is a noise gap in it
Higher-order semantic and syntax knowledge is used to fill the blanks
What is a phoneme?
A unit of sound that distinguishes one word from another in a particular language
Why was the international phonetic alphabet (IPA) developed?
To avoid confusing differences between sound and spelling
Describe the process of phonation
Process through which vocal folds are made to vibrate when air pushes out of the lungs
At which point in respiration does air reach the vocal cords?
Once air reaches the larynx
How does size of your vocal folds affect the sounds you make?
Smaller vocal folds = higher pitched sounds
What kind of pattern does the spectrum of sound passing through the vocal folds produce?
A harmonic spectrum
What information does phonation provide?
The pitch of the sound we are producing
What is articulation?
The act or manner or producing a speech sound using the vocal tract
What structures compose the vocal tract?
Oral + nasal tract
how can humans change the shape of their vocal tract?
By manipulating their jaws, lips, tongue, body, tongue tip, and velum
How do you create resonance characteristics of speech?
By changing the size and shape of the vocal tracts to affect sound frequency distribution
What do we call peaks in the speech spectrum?
Formants
What are formants?
Vowel outputs that result from combining the harmonic spectrum with a filter function
Formants have ______ (higher/lower) frequencies for people who have shorter vocal tracts
higher
What is coarticulation?
When you are pronouncing multiple vowels or consonants at the same time as a result of speech production being very fast
How does categorial perception help solve the problem of coarticulation?
It helps us perceive sounds that are different as belonging to the same phoneme category
What is the motor theory of speech perception?
Motor processes used to produce speech sounds are used in reverse to understand the acoustic speech signal
What is the McGurk effect?
What someone sees can effect what they hear
What is the problem with motor theory?
Speech production is as complex, if not more complex, than speech perception
TRUE/FALSE
sound distinctions are specific to various languages
true
Where in the brain does phonetic discrimination take place?
In the belt and parabelt areas surrounding the primary auditory cortex
What brain area is responsible for assembling phonemes to form words and retrieve the semantic meaning of the words?
Wernicke’s area
Describe Wernicke’s aphasia
These patients do not have trouble producing speech, however the words they use will be wrong. When they hear speech, they will accessing the semantic meaning of the wrong word which causes them to mix up the words they hear as well
What do patients who have Broca’s aphasia struggle with?
Producing speech
What is causing people with Broca’s aphasia to have trouble speaking?
They have trouble with the complex coordination of different motor movements of the lips, tongue, etc. that is necessary for producing speech
Which hemisphere do you almost always find lesions in Wernicke’s or Broca’s areas?
Left
What is the hypothesis for the meaning of music?
May help with social cohesion
Define tone height
A sound quality corresponding to the level of pitch
Define tone chroma
A sound quality shared by tones that have the same octave interval
What is an octave?
The interval between two sound frequencies having a ratio of 2:1
How many octaves are in the audible range?
10
What is consonance?
The combinations of sounds is pleasant, as if the notes “go together”
What is dissonance?
The combination of sounds is unpleasant or “off”
When does consonance occur?
When the fundamental frequency of the two notes have a simple ratio (e.g., 3:2 or 4:3)
When two notes coincide, what happens to the frequencies?
They join to form a note with a lower frequency
When does dissonance occur?
When the fundamental frequency of two notes gave a complex ratio (e.g., 42:33)
What is a scale?
A particular subset of notes in an octave
What is a key?
The scale that functions as the basis of a musical composition
How do you differentiate between major and minor scales?
By the pattern of intervals (number of semitones) between successive notes
In general, major scales sound _____ (happy/sad) and minor scales sound ______ (happy/sad)
happy, sad
What is the root note of a key?
Acts as the gravity point of the key (e.g., the root note of C minor is C)
What is a melody?
A sequence of notes or chords perceived as a single coherent structure
How do you define melodies?
By their contours (aka the pattern of rises and declines in pitch)
Where in the brain is music processed?
In the right auditory cortex, in the belt and parabelt areas of the right temporal lobe
What is congenital amusia?
An umbrella term for lifelong musical disabilities that cannot be attributed to intellectual disability, lack of exposure, or brain damage after birth
What is an early right anterior negativity (ERAN)?
A negative event-related potential that occurs 200ms after the detection of a melodic tonal violation
Where are ERANs thought to be produced?
In the belt and parabelt region of the superior temporal gyrus
What is a P600?
A positive event-related potential that occurs 600ms after the detection of a melodic tonal violation
Where are P600s thought to be generated?
in the inferior frontal gyrus in the homologous regions of Broca’s area in the right hemisphere
What do P600s reflect?
Conscious perception of a tonal violation
Amusics have normal ERANs, but have no P600. What does this suggest?
Suggests they lack conscious access to processed pitch deviances
What is absolute pitch?
A rare ability whereby people are able to very accurately name or produce notes without comparison to other notes
