L7 hearing things Flashcards
What is the sound/signal emitted by an object/system when hit ?
Impulse response
What is the fundamental ingredient of complex sounds?
Sine wave
What is the rate mass-spring systems like to vibrate at?
A rate proportional to the square root of their ‘stiffness’ and inversely proportional to their weight
In resonant cavities, what will happen to the ‘lumps of air’ at the entrance/exit of the cavity?
It will oscillate under the elastic forces exercised by the air inside the cavity
What is the preferred resonance frequency?
Inversely proportional to the square root of the volume
What is the relationship between resonators and sounds?
Positively related, e.g. larger resonators, deeper sounds
What kind of physical properties are reflected in the frequency spectra they emit when they make sounds?
Size, mass and stiffness
What is the job of ears?
Perform a time-frequency analysis of incoming sounds
What is the characteristics of basilar membrane?
Stiff at the base, floppy at the apex
How will vibrations travel?
From the stapes to the round window and either take a short route through stiff membrane or a longer route through more inert fluid
Describe the routes (inertia, stiffness)
Shorter route: lower inertia, higher stiffness
Longer routes: Higher inertia, lower stiffness
Characteristics of helicotrema
No resistance from basilar membrane
Higher sound frequency will go to which place in the basilar membrane?
Nearer to the base
What will outer hair cells fire?
Resting potential (X action potential)
Describe the axons sent to the brain by outer hair cells.
Not myelinated and in small numbers
Why do outer hair cells jiggle?
To amplify the vibrations by dancing along to the sound
Advantages of jiggling outer hair cells.
Easier for encoding and picking up by inner hair cells
Where do hair cells locate?
Organ of Corti
What do hair cells transduce?
Mechanical vibration of the basilar membrane into electrical signals
Where do inner hair cells transmit the signals to?
Auditory nerve fibres
What are outer hair cells?
Mechanical feedback devices which amplify the signal on a tuneable manner
When hearing researchers talk about sound frequencies, what do they refer ‘event rates’ to?
Fourier (sine wave) components
Waves have several frequencies according to? (one of each Fourier component sine wave that has non-zero amplitude)
Fourier spectra
What can the frequency filtering by the basilar membrane can do, to some extent? (Fourier analysis)
‘Decompose’ complex sounds into its constituent frequency components
What will happen if a complex sound had many frequency components?
The spatial resolution of this ‘place code for frequency’ becomes quickly overwhelmed
Definition of “Harmonics”
The frequency components are all integer multiples of a lowest, common ‘fundamental’ frequency
What do physical objects tend to have, what would that lead to?
Modes of vibration leads to sounds with many frequency components, ‘overtones’ (harmonics)
Describe noise-like sounds
Irregular, non-periodic sounds, no harmonic structure
What are human speech comprise of?
Both periodic (voiced) and non-periodic, noise-like (unvoiced) speech sounds
What does the Fourier Transform encourage us to think of a click?
An infinite series of sine waves, which have started at the beginning of time, continue until the end of time, and all happen to pile up at the one moment when the click occurs
How a click train is perceived when frequencies up to ca 30-50 Hz?
Isolated event
How a click train is perceived when frequencies above ca 30-50 Hz?
Individual clicks combine, and perceive as a continuous hum with a strong pitch
Articulators’ movement will ?
Change resonance properties of the vocal tract
What do formants do?
Encode frequencies on broad scale
What do harmonics do?
In fine scale, know which pitch they are ranging (voice tones)
It is whose job to produce a spectrogram of the incoming sound?
Ear
It is whose job to interpret the spectrogram to identify sounds?
Brain
What do auditory nerve discharge rates depend on?
The amount of sound energy near the neuron’s characteristic frequency
What is tonotopy?
A place coding for frequency because of basilar membrane tuning
What is phase locking?
The discharge of cochlear nerve fibres to low-frequency sounds occur at particular times
What do phase locking do?
Encodes information about the temporal structure of sounds that is used for hearing of pitch and spatial hearing
What is the auditory pathway?
Nuclei in the brainstem (cochlear and superior olivary nuclei) and midbrain (lateral lemniscus and inferior colliculus) then thalamus
Describe the tonotopy in the cochlear nucleus
The base of the basilar membrane projects to the medial cochlear nucleus, the apex to lateral cochlear nucleus
What is the relationship between iterated rippled noise and periodicity?
Increasing the number of iterations can make iterated rippled noise more periodic, vice versa.
What is the relationship between signal periodicity and pitch?
The less periodic the signal, the weaker the pitch
Neurons in the midbrain or above show much less_________ to amplitude modulated signals than neurons in the _____
phase locking; brainstem
Periodicity maps in midbrain: transition from a _____ to a ___ code
timing; rate
Some neurons have _______ and exhibits _______ (____)
bandpass MTFs; best modulation frequencies; BMFs
Topographic maps of BMF may exist within _______ of the inferior colliculus, “periodotopy”
isofrequency laminae
Baumann et al described periodotopic maps in monkey IC obtained with fMRI. They used stimuli from _____Hz (____) to _____Hz (_____). Their sample size is quite ____. The observed orientation of their periodic map (______) appears to differ from (_____)
0.5; infra-pitch; 512; mid-range pitch; small; medio-dorsal to latero-ventral for high to low; predimonantly caudal to rostral
In marmoset, pitch sensitive neurons are most commonly found on the boundary between ____ and ____
A1; R
What sounds are periodic?
Pitchy sounds
Pitchy sounds means they have many _____ frequency components
harmonic
Missing fundamental stimuli show that there is no straight-forward relationship between _________ and ________.
tonotopy; perceived pitch
_______ of periodicity is important
Temporal encoding
What should we be skeptical of?
The notion of pitch neurons in the brain
Interaural time difference cues are powerful cues to _______, but they are ______ (____)
sound source direction; ambiguous; cones of confusion
Interaural level cues are_________, unlike ITDs
highly frequency dependent
At _____ sound frequencies ILDs tend to become _____, more____, and hence more ________
higher; larger; complex; informative
What is the cue that even people with one deaf ear can also have?
Spectral (Monaural) cues
Spectral (Monaural) cues can tell sounds coming from _______ to ______
top; bottom
‘Type IV’ neurons in the ______ often have _____ frequency response areas with ______ sidebands. This makes them sensitive to ‘________’ like those seen in ________.
dorsal cochlear nucleus; inhibitory; excitatory; spectral notches; spectral localisation cues
Some reports suggest that anterior cortical belt areas may more selective for _____ and less for _____, while _______ are more location specific.
sound identity; sound source location; caudal belt areas
It has been hypothesized that anterior cortical belt& caudal belt areas may be the starting positions for a ventral ‘what’ stream heading for ______ and a dorsal ‘where’ stream which heads for ____
inferotemporal cortex; postero-parietal cortex
Deactivating some cortical areas (A1, PAF) by ____, impairs ______ but impairing others (AAF) does not
cooling; sound localization
Our brain processes binaural (ITD and ILD) and spectral cues to determine _______
sound source direction
The brain’s ____ sensitivity is remarkably precise, down to ____ of microseconds
ITD; tens
The _______ are brainstem nuclei where binaural information about ILDs and ITDs respectively is _____ computed
lateral and medial superior olive; first
Higher up in the brain, information from different cues and pathways in ____. Except for the ______, there is no ‘______’ in the _______ brain
combined; superior colliculus; map of auditory space; mammalian
The degree to which different cortical areas specialize in ______ is controversial
spatial hearing
Speech sounds are created when vibrating _______ or _____ or ______ of the vocal tract excite ‘_____’ resonances in cavities in our vocal tracts
vocal folds; temporary; partial obstructions; formant
Change in vocal fold vibration _______ -> pitch change, important for ____, ____, voice tone in tonal languages. Pitch not important in semantics in _______ languages
frequency; melody; prosody; Indo-European
Change in ______ (formants) through ‘_____’ is responsible for most of the _______ in speech. (Dynamics also play a role, e.g. ‘voice onset time’
resonances; articulation; semantic category distinctions
Brain transforms ____ to ____ to _____ information as information travels from _____ to _________ and on to many other brain regions
acoustic; phonemic; semantic; primary auditory cortex; superior temporal gyrus
Primary cortex is on _____
Heschel’s Gyrus
Human superior temporal gyrus is sensitive to _______ such as ‘manner of articulation’
phonetic feature
Mitchell et al argued that words which have similar meanings according to a statistical semantic analysis should produce_______ in those parts of the brain involved in ________.
similar brain activations; interpreting meaning
Mitchell et al built a predictive model which was able to predict evoked brain activity over large parts of the brain, including ____ and _____ lobes, fusiform and _________, medial frontal gyrus and anterior cingulate.
bilateral occipital; parietal; middle frontal gyri
