W4: Audition Flashcards

Question

two-tone suppression

Answer 1

Audition: Physics/Biology: Stimulus: Complex Waves “Suppression of an auditory nerve fiber’s response to a tone during presentation of a second tone.” When the second tone lies outside the fibers dynamic range.

Answer 2

Audition: Physiology (incl. outer, middle and inner ear) detects/interprets sound pressure waves. Outer ear is only visible part. Inner ear creates and transfers neural responses to the central auditory system (“population of neurons in brainstem and cerebral cortex” ). Peripheral system is well understood, less understood is how the central auditory system converts the neural response into auditory perception.

Answer 3

Audition: Physiology (incl pinna, meatus and ear canal) detects and transfers energy down ear canal

Answer 4

Audition: Physiology: outer ear shapes and ridges create reflections which are used as comparison stimuli to create monaural cues to detect the location of sound along a vertical plane. immobile “flexible flap” consisting of cartilage and ligaments and muscles which connect the ear to the skull. shapes and ridges create reflections which are used as comparison stimuli to create monaural cues to detect the location of sound along a vertical plane.

Answer 5

Audition: Physiology: outer ear opening of the ear which sends soundwaves down the ear canal

Answer 6

Audition: Physiology: outer ear carries sound pressure waves through ear. Consists of the tympanic membrane/ear drum

Answer 7

Audition: Physiology: outer ear Concha: inner funnel/”bowl-shape” structure of outer ear

Answer 8

Audition: Physiology: outer ear “Amplifying sound pressure for medium frequencies between 1500 and 7000 Hz” “Folds of pinna (acoustic filter) attenuates high frequency sound components”

Answer 9

Audition: Physiology: Mid ear “The air-filled cavity” housing ossicles and “associated supporting structures” which sends soundwaves from the eardum/tympanic membrane to the oval window of the cochlea (via impedance matching - which makes mid ear a linear transmitter)

Answer 10

Audition: Physiology: Mid ear: Ossicles: three bones in middle ear; connecting TM/eardrum to cochlea, and “maximise transmission of sound from air pressure waves of outer ear to fluids in inner ear” - impedance match incus Malleus: “head” connects to TM/eardrum, “handle” connects to incus Stapes: (smallest bone in body) connects to the incus and oval window of the cochlea - it pushes in and out to send vibrations through/displace to the fluids in the labyrinth (perilymph) and the inner ear (endolymph) Estachian Tube: connects mid-ear chamber to the nasal cavity to control air pressure within the chamber by draining the fluids created by T.M. Oval Window: “membrane-covered opening of the cochlea” connects stapes to cochlea. This window gives flexibility to the ossicles in order to send vibrations through the perilymph, displacing the endolymph/fluid within the inner ear/cochlea

Answer 11

Audition: Physiology: Mid ear: “The degree of resistance offered by a medium (air or fluid) to an oscillating signal… air and fluid differ by acoustic impedance” why the middle ears job is to “maximise transmission of sound pressure waves of outer to inner ear” by applying impedance matching

Answer 12

Audition: Physiology: Mid ear: “The boost in pressure at the oval window provided by the mechanical properties of the middle ear, it matches up the differing acoustic impedances of air and inner-ear fluid.” (air in ™ has lower acoustic impedance, oval window = higher acoustic impedance due to fluid in cochlea)

Answer 13

Audition: Physiology: Mid ear Ways that Middle Ear do Impedance Matching: The force/unit area of stapes is significantly higher than T.M’s (as stapes area is 17 times smaller) therefore creating a large force onto the oval window Ossicles boost mechanical force at T.M *”together they increase pressure by 33 dB SPL.”

Answer 14

Audition: Physiology: Inner ear “The fluid-filled organ lying in the temporal bone, containing mechanoreceptors for hearing and balance.” considered to be an “inertial guidance system, acoustic amplifier, and frequency analyzer”. Vestibular organ senses body movement and position. Cochlea is the auditory sense organ which converts sound pressure waves into neural impulses.

Answer 15

Audition: Physiology: Inner ear auditory sense organ in which mechanoreceptors convert sound pressure waves into neural impulses. In the shape of a coiled tube (10mm diameter, 34mm long), which minimizes space, “maximises the supply of blood and nerves, and boosts its response to low frequency sounds” The tube is divided into three chambers - the scala vestibuli and scala tympani which is separated by the scala media located within the cochlear partition.

Answer 16

Audition: Physiology: Inner ear: Cochlea first tube of cochlear which includes the oval window.

Answer 17

Audition: Physiology: Inner ear: Cochlea at the end of the cochlear with a round window

Answer 18

Audition: Physiology: Inner ear: Cochlea separated vestibuli and tympani, located within the cochlear partition

Answer 19

Audition: Physiology: Inner ear: Cochlea includes SM and BM; and separates SV and ST

Answer 20

Audition: Physiology: Inner ear: Cochlea located in cochlear partition, which has hair cells and mechanoreceptors. Part of organ of corti.

Answer 21

Audition: Physiology: Inner ear: CochleaT.M. transfers sound vibrations to stapes - “stapes push back and forth on oval window at same freq. As sound wave” - stapes hitting oval window - displaces scala vestibulis fluid = traveling wave down BM - transfer pressure to scala media - displaces cochlear partition - transfer vibrations to scala tympani - deforms BM *pressure is sent through chambers when stapes pulls back from oval window

Answer 22

Audition: Physiology: Inner ear: Cochlea: Mechanical Properties caused by displacement of BM when sound waves hit oval window. wave travels through the part of BM with max displacement. Starts at basal end of membrane to the apical end

Answer 23

Audition: Physiology: Inner ear: Cochlea: Mechanical Properties cochlear fluid displacement = vibrations along BM. vibrations freq determines location of max displacement (low freq near apical end (wider/flexible), high freq near basal end near staped (narrow/stiff) - how cochlear codes freq.) - location codes freq.

Answer 24

Audition: Physiology: Inner ear: Cochlea: Mechanical Properties a small band of frequencies cause max displacement - similar frequencies require much more sound to create the same amount of displacement.

Answer 25

Audition: Physiology: Inner ear: Cochlea: Mechanical Properties at extremely high or low amplitudes, amplitude of BM doubles when amplitude of input wave does When two pure sinusodal tones with vastly different frequencies enter the membrane together, their separate locations of displacement should match their frequencies (if close in freq, creates one larger nonsinusodal displacement)

Answer 26

Audition: Physiology: Inner ear: Cochlea part of cochlear partition. Includes stereocilia between BM and T.M

Answer 27

Audition: Physiology: Inner ear: Cochlea flexible structure above the BM. holds other stereocilia

Answer 28

Audition: Physiology: Inner ear: Cochlea: mechanoreceptors mechanoreceptors/sensory hair cells that are organised into four neat rows along the BM. one row is inside the cochlear spiral, the other rows are closer to the outside of spiral

Answer 29

Audition: Physiology: Inner ear: Cochlea: mechanoreceptors “The mechanoreceptors on the basilar membrane that provide afferent signals to the auditory system when the membrane is displaced.” a row of approx. 3500 hair cells that are located inside the cochlear spiral, along BM Conveys most sensory info on sound. “The base of each inner hair cell makes synaptic contact with (10) afferent fibers of the auditory nerve. = 90-95% of afferent fibres” Fluid displacement makes BM vibrate = shearing motion > deflects inner hair cells stereocilia = inner hair cell base sends an electric impulse to afferent fibers which carry impulse to brain BM moves twrds T.M = Displace twrd tallest stereocilia = depolarized hair cell that sterocilia is embedded into = release neurotransmitter = voltage increase = electrical impulse BM away from T.M = Displace twrd smallest stereocilia = hyperpolarized cell = voltage decrease small displacements cause enough potential to reach the threshold of hearing. Transduction can happen within 10 microseconds

Answer 30

Audition: Physiology: Inner ear: Cochlea: mechanoreceptors “Motile hair cells spanning the gap between the basilar membrane and tectorial membrane; they control the mechanical coupling between the two membranes. (MC: amplifies inner hair cells and BM response)” three rows of 12000 hair cells, close to outside spiral. Motile response/changing length: either by contracting from proteins in the cell when stereocilia is displaced or by “receiving effervent stimulation from the cochlea nerve” efferent fibres send signals to cochlea from central auditory system. *”this increases BM’s mechanical sensitivity and narrow freq response” *fluid vibrations that displace the BM, displace the tectorial membrane - displacing inner hair cells in fluid, and displacing tips of outer hair cells through the motion of the membranes

Answer 31

Audition: Physiology: Inner ear: Cochlea: Sound Freq. Coding (Aud nerve) “intracellular resting potential of hair cells is –70 mV.” Hair cells are depolarized/increased voltage when BM moves towards T.M, cells are hyperpolarised as BM moves away from ™. ^ depolarized cells release neurotransmitters

Answer 32

Audition: Physiology: Inner ear: Cochlea: Sound Freq. Coding (Aud nerve) “The firing of hair cells in synchrony with the variation of pressure in a sound wave (during positive phase)” - for low freq. Waves Sound freq. Higher than 1kHz = auditory nerve fibres cannot fire at every cycle but still phase-locked. Phase locking stops at 4-5 kHz Ways to encode freq. Of sound waves as they enter ear

Answer 33

Audition: Physiology: Inner ear: Cochlea: Sound freq Coding (Aud nerve) is based on frequency-to-place conversion. Area of max displacement/max hair cell activity = characteristic frequency of sound Characteristic Frequency: max activity of cells reflect the frequency cells are tuned to in that area, similar freq receive more reduced response

Answer 34

Audition: Physiology: Inner ear: Cochlea: Sound Freq. Coding (Aud nerve) due to phase-locking, auditory nerve fiber/inner hair cell impulse rate reflects frequency. Impulse doesnt reflect magnitude as fibers response decrease over time due to adaptation Phase locking: auditory nerve fiber impulses fire at same phase - rate of impulse therefore reflects frequency of wave Volley Principle: ‘combined response of ensemble of nerve fibres should reconstruct the frequency of the wave.’

Answer 35

Audition: Physiology: Inner ear: Cochlea: Intensity Coding (Aud nerve) steady firing rate of nerve fibres without stimulation, rate varies across different nerve fibres, most ranging from higher rates 18-250 spikes/second.

Answer 36

Audition: Physiology: Inner ear: Cochlea: Intensity Coding (Aud nerve) “In auditory nerve fibers, it is the difference between the minimum SPL to which a fiber responds, and the SPL at the fiber’s maximum firing rate.” increases in SPL will cause no changes to fibers firing rate. Auditory nerve fibres: 20 - 60 dB. Human range is 100dB - covered by two fiber sets: ^”fibers w/ high spontaneous firing rate = low threshold (30-40dB); DR = 60 dB SPL Low spontaneous firing rate = high threshold (50dB); DR = 100 dB SPL ^’different affervent fibres (connect to inner hair cells) carry different sound intensity levels’ Characteristic Frequency: fibers respond best to certain frequencies (req low amp) and respond lesser to similar frequencies (w/ higher amp) - reflects location on BM - this frequency tuning is reflected in tuning curves, proving that auditory nerves are band-pass filters

Answer 37

Audition: Physiology: Pathways: Ascending in the cochlea are associated with the auditory nerve. These cells create auditory nerve fibers when they contact 1+ hair cells.

Answer 38

Audition: Physiology: Pathways: Ascending “form synapses with large groups of neurons in the cochlear nuclei in the brain stem” start on one side of the ears cochlea, then go to the nucleus on the same side, for most to then be sent to the cortex on the opposite (contralateral) side of the brain. The remaining fibers stay on the same (ipsilateral) side of the brain. “One group of fibers from each cochlear nucleus ascends directly to the contralateral inferior colliculus in the midbrain.” another group only go to superior olive in the pons (most going to the contralateral one). Then to the lateral lemniscus, then inferior colliculus, then medial geniculate, then to their associated side of the primary auditory cortex.

Answer 39

Audition: Physiology: Pathways: Ascending “The complex of cells in the brainstem receiving projections from the cochlear nucleus; it contains binaural neurons that provide information about the location of sound sources.”

Answer 40

Audition: Physiology: Pathways: Ascending “The obligatory relay station for all ascending projections in the auditory system, en route to the cortex.” in thalamus

Answer 41

Audition: Physiology: Pathways: Ascending “involves a complex combination of serial and parallel processing stages.” what and where processing

Answer 42

Audition: Physiology: Pathways: Ascending

Answer 43

Audition: Physiology: Pathways: Ascending “What” Processing: “What” Sound Attributes: ‘frequency composition, temporal features (incl. Phase properties, onset and duration)’ Frequency: responded to by neurons in cochlear nuclei (wider DR than fibers) “What” information: conveyed by cells in the medial geniculate nucleus and inferior colliculus “responding only to sounds coming from one ear (monaural) that vary in frequency, or sounds of a specific duration.” sent to cortex from MGN ^”some of these cells respond to multiple sensory modalities, incl. Somatosensory vestibular and visual systems”

Answer 44

Audition: Physiology: Pathways: Ascending “Where” Processing:... Sound localisation: helps locate sound source or distinguish sounds from sources. ‘Pinna filtering effect locates sound sources in vertical plane’ Location of ears of each side of head helps locate sound sources in azimuth plane ^ sound sources side of head indicated by the ear the sound gets to first. The other signal that reaches the contralateral ear can appear different if attenuated as it travels behind the head. “Specialized neural circuits in the auditory pathway detect the very small differences in phase and intensity that can be used for sound localization.”: Phase: Circuits in the medial superior olive compute the interaural time differences (ITD) between the auditory signals arriving at the two ears. Intensity: Circuits in the lateral superior olive compute the difference in intensity between the signals arriving at the two ears (interaural level differences , or ILD). Azimuth: refers to horizontal plane

Answer 45

Audition: Physiology: Pathways: Ascending ‘sound source directly in front of one ear arrives at the opposite ear 700 ms later. ITD decreases as sound source moves to front/behind head.’ ITD detection threshold: 10ms

Answer 46

Audition: Physiology: Pathways: Ascending head attenuates frequencies over 2kHz, resulting in higher frequency signal reaching the ipsilateral ear, which neurons in lateral superior olive respond to - these neurons are EI (meaning they receive and inhibitory (from ipsilateral anteroventral cochlear nucleus) and excitatory signals (from contralateral anteroventral cochlear nucleus) ^net response of these neurons depend on the levels of each signal. Strongest response = when the signal is on the same side of the head Weakest response = when signal is in median plane of head (front/behind) as the e and i signals cancel eachother out ^this response is sent through the inferior colluculus, medial geniculate nucleus to cortex Therefore “Some cells in the inferior colliculi respond to either ITD or ILD” Head/Acoustic Shadow: area surrounding the further ear to noise, where sounds that reach this area decrease in intensity as the head attenuates these signals

Answer 47

Audition: Physiology: Cortex located on superior temporal lobe, includes ‘three core areas with different maps of frequency space, and cells within these areas respond well to pure tones and have a narrow frequency tuning (small range of preferable frequencies)

Answer 48

Audition: Physiology: Cortex “Two concentric bands of cortex encircling primary auditory cortex, containing cells responsive to auditory stimuli.” “Cells in this region respond better to narrowband noise and frequency-modulated sweeps”

Answer 49

Audition: Physiology: auditory association Cortex Belt region: surrounds the primary auditory cortex Parabelt region: surrounds the belt region. “Anterior area projects the “what” pathway to orbitofrontal cortex, posterior part projects the “where” pathway to posterior parietal cortex and dorsolateral prefrontal cortex”

Answer 50

Audition: Physiology: Cortex Tonotopic Organization: “An organized arrangement of neurons, so that cells with similar frequency preferences lie close together in a neural structure.” Isofrequency bands: “The cortical surface can be divided into a series of bands containing cells with the same characteristic frequency… Cells within a column extending down from the surface of the cortex have similar characteristic frequencies.”

Answer 51

Audition: Physiology: Cortex Lesion Studies: Deficit in “where”: parietal, frontal and superior temporal cortex Deficit in “what”: fusiform and temporal cortex

Answer 52

Audition: Physiology: Cortex Isofrequency bands: “The cortical surface can be divided into a series of bands containing cells with the same characteristic frequency… Cells within a column extending down from the surface of the cortex have similar characteristic frequencies.”

Answer 53

Audition: Physiology: Descending Pathway Route: cortex– medial geniculate nuclei– inferior colliculi– superior olives– cochlear nuclei– cochleas outer hair cells

Answer 54

Audition: Physiology: Descending Pathway alters sensory input, “ability to attend selectively to certain auditory stimuli.”

Answer 55

Audition: Physiology: Descending Pathway amplifying inner hair cells, middle ears acoustic reflex

Answer 56

Audition: Physiology: Descending Pathway Efferent pathway: Outer Hair Cells receive top-down information/descending projections from the cortex to “regulate hearing aspects such as amplification, auditory attention and acoustic reflex of inner ear”. More outer hair cells than inner but only 5-10% connect to nerve fibers Motile response occurs when they receive efferent signals - source of cochlear amplifier “Descending projections may be involved in auditory attention & outer hair cell amp functions”

Answer 57

Audition: Perception pitch, loudness and spatial hearing

Answer 58

Audition: Perception: Pitch perceptual attribute that = frequency of pure tone, fundamental frequency of complex tones. Orders musical notes from low bass to high treble.

Answer 59

Audition: Perception: Pitch in particular circumstances the ear can decompose a complex soundwave from an instrument into “separate representation for each frequency component” : “the prime partial tone” (fundamental frequency) “and the various partial upper tones” (harmonic series) Psychophysical Studies of Freq Selectivity: investigating its limits.

Answer 60

Audition: Perception: Pitch Psychophysical Studies of Freq Selectivity: investigating its limits. Masking: main technique to examine limits ^. Experimental procedure where a noise mask (complex soundwave including tones with same amp but different frequencies and phases = hissing noise) impacts participants detection of a sine wave

Answer 61

Audition: Perception: Pitch Band-Pass Noise: when a complex tones individual frequencies range within a bandwidth around the center frequency (e.g. “band-pass noise with a center frequency of 2000 Hz and a bandwidth of 400 Hz contains energy at all frequencies between 1800 and 2200 Hz”) *center freq = indv sine wave to be detected against mask The sine wave gets harder to detect as bandwidth increases until a certain point where detection abilities stay constant - due to band-pass filters in auditory system. This filter’s center frequency would be similar the sine signals freq, and noises that produce a masking effect must fall within the filter’s critical bandwidth Critical Bandwidth: is the bandwidth of a filter which ends at the point of bandwidth where this level and further increase does not alter detection threshold/abilities.

Answer 62

Audition: Perception: Pitch Pure Tone Masks: have also been used where signal freq is set low (e.g. 10 dB SPL) and pure tone mask is modified in equal increments (systematic) until signal freq is detected - the results create a psychophysical tuning curve (meaning that masks do best when their freq is close to the signals. The more different their frequencies are, the higher the required SPL is for it to mask signal freq). This suggests that we possess many band-pass filters with different ranges of critical bandwidths which overlap in order to detect a large range of frequencies.

Answer 63

Audition: Perception: Pitch Critical-Band Masking: masking of a sine signal occurs if noise masks frequency is within the critical bandwidth. Assumptions: ‘A signal increases activity in auditory fibers tuned to it’s freq Signal is detected if this activity reaches a certain threshold Mask will cause activity in filter irrelevant to signal *the mask will only have an effect when activating same fibers as signal if masks activity passes the same detection threshold for the signal- the masks activity will counteract the signals activity, preventing detection of the signal.

Answer 64

Audition: Perception: Pitch are required to explain our small discrimination threshold. Links patterns across freq-tuned neurons (which reflects the type of sound stimulus) and auditory fibers to perception of pitch. Place and rate coding theories for pure tones temporal and pattern regocnition theory for complex waves

Answer 65

Audition: Perception: Pitch Place and rate coding theories for pure tones Evidence for both theories: rate and place code is used for lower- mid freq tones (up to around 4-5kHz)

Answer 66

Audition: Perception: Pitch temporal and pattern regocnition theory for complex waves

Answer 67

Audition: Perception: Pitch auditory system as fourier analyser - freq-tuned filters respond to each component wave of complex tone - area of activated filters reflects sine wave frequency high freq/pitch tones = base of BM near oval window; low freq/pitch tones = apex (at end of cochlear spiral) - ^ perceived pitch = fundamental frequency = sine wave w/ freq closest to apex. *pitch discrimination thresholds depends on filters characteristic frequency and bandwidth (measuring bandwidths help us understand filter’s discrimination threshold - bandwidths start narrow and increase with frequency (why its harder to discriminate between higher frequencies)) ^this goes against place theory which assumes that bandwidth and freq discrimination remain constant

Answer 68

Audition: Perception: Pitch Auditory nerve responses are phase locked (they fire at same point of phase in each cycle) to frequencies of waves below 5kHz - therefore response rate reflects frequency of sound. Theory proposes that pitches with differing tones are discriminated by “differences in the response rate or time intervals between neural firings.”

Answer 69

Audition: Perception: Pitch Missing Fundamental Wave: when one can determine a tones pitch in the absence of the fundamental frequency (e.g. fundamental frequencies of males voices cannot be produced by phone) as the brain fills it in (the sound appears hollow/higher pitch due to absence of bass/FF).

Answer 70

Audition: Perception: Pitch Temporal Theory: explains how beats of unresolved harmonics create a residue pitch which reflects the sound of the missing fundamental frequency. Up to 1kHz = Phase locking determines pitch Up to 4kHz = Volley Principle determines pitch: fibers combined response = freq Residue pitches determine pitch for Higher frequencies: unresolved harmonics (multiple harmonics that are indiscriminable due to falling within the same filters bandwidth) - overlapping of these harmonics creates a residue pitch with beats - timing reflects the missing fundamental frequency Residue Pitch: is the sensation of pitch created and encoded by the beats of higher unresolved harmonics. Beats: unresolved harmonics (two indistinguishable harmonics sound as one due to falling within the same filter bandwidth) overlap and beat at a frequency that reflects their fundamental frequency. The auditory nerve fires encode pitch by phase locking to the residue pitch (rate coding) *criticism: people tend to depend on the different pitch created by resolved harmonics. Need theories that apply to resolved and unresolved harmonics such as the following…

Answer 71

Audition: Perception: Pitch Pattern Recognition Theory: pitch = fundamental frequency of resolved harmonics by using place coding Explains missing fundamental effect: ff determined by the distance between harmonics Criticism: doesnt explain unresolved harmonics

Answer 72

Audition: Perception: Pitch ‘unsure how auditory nerves temporal code influences cortical neurons frequency tuning’ Unsure how Tonotopical mapping (like frequency-to-place conversion in BM) of primate cortex’s allows pitch to be encoded Pitch centure may be in secondary auditory cortex but unsure

Answer 73

Audition: Perception: Loudness relates to SPL intensity and amplitude. The following 2 are comparison techniques:

Answer 74

Audition: Perception: Loudness is a plot of various comparison (freq) stimuli, being described in dB SPL (i.e. a certain amount of dB above or below the standard pressure level) - SPL being the standard stimulus. Shows how different amplitudes (dB SPL) can have the equal loudness due to variation in frequency (kHz). Lowest curve = absolute threshold for tones at that freq./hearing in general (at around 3dB) ‘Low freq = poor sensitivity - requires higher amp for equal loudness Mid freq = high sensitivity - low amp High freq = medium sensitivity - medium amp < curve flattening out

Answer 75

Audition: Perception: Loudness participant applies magnitude estimation (chptr 1) to sounds of various intensities to understand “how loudness scales with intensity”. Non-linear increase of loudness by intensity - in accordance with stevens power law, loudness exponent = 0.3 (intensity ^ 10dB, loudness ^ 2 (for 40 dB SPL and above))

Answer 76

Audition: Perception: Auditory Localization Two types of planes can be used to locate the source's direction: horizontal plane is described in “azimuth angle relative to straight head” and uses binaural cues vertical plane is described “by an angle of elevation relative to horizontal.” uses monaural cues (e.g. source w/ azimuth angle of 0° and elevation angle of 90° = right above head)

Answer 77

Audition: Perception: Auditory Localization Azimuth angle and binaural cues

Answer 78

Audition: Perception: Auditory Localization: horizontal plane “The smallest change in the azimuth angle of a sound source that can be detected reliably.” *JND of sound based on differences along azimuth angle All angles struggle to detect diff arond 1500-1800 Hz - is the transition freq period where ITD and ILD both struggle to encode location.

Answer 79

Audition: Perception: Auditory Localization: horizontal plane ITD for low freq, ILD for high freq because ILD struggle to examine small diff between low frequencies as they can easily pass through the head/not attenuated ITD: arrives at closer ear first - ‘diff in arrival depends on azimuth angle’ (max ITD = 650ms, 180 degree travel, ITD = 0 in front/behind head - shows that two azimuths share the same timing). applied to low frequency sounds. ‘Processed in brainstem, medial superior olive’ ILD: higher frequencies dont pass through head and therefore lie in the acoustic shadow of the opposite ear, attenuating the further freq = discrimination detection ILD = 0 in front/behind head - same intensity/travelling ‘Processed in brainstem, Lateral superior olive’

Answer 80

Audition: Perception: Auditory Localization: horizontal plane “A cone of space extended from a listener’s head, defining the directions that produce the same interaural time difference and are therefore confusable.” e.g. the front and back of the head ^RESOLUTION: moving head around decreases size of cone and use of vertical cues helps define elevation.

Answer 81

Audition: Perception: Auditory Localization: Vertical plane much better judgment of location based on monaural cues - created by the pinna working as an acoustic filter for amp and phase. Two main effects of the pinna: Pinna only allows short wavelengths in above the frequency of 6 kHz Adds peaks and valleys (happens to higher frequencies when the sound is more elevated)

Answer 82

Audition: Perception: Auditory Localization: Vertical plane deciding the location of fused sounds (multiple sounds that occur 5-50ms apart sound like one sound) based on the direction of the first/direct component of fused sound (as they are less likely to be reflecting off other objects in different directions) or by comparing the “difference between the direct and reflected sound” (from pinna filtering/reflecting)

Answer 83

Audition: Perception: Auditory Localization: Vertical plane four cues are used to determine distance: Distance-to-intensity ratio: Closer sounds = louder - ‘distance doubles: sound decreases by 4’ Direct-to-reverbant energy ratio: In places where sound reflects off surfaces - amount of sound not directly hitting ear (i.e. bouncing off other surfaces) increases with distance More distant sounds are more muffled: “Air molecules absorb energy at higher sound frequencies more” Within a meter, ILD decreases as distance increases - isnt this the first point? *studies show these cues underestimate and their effectiveness depends on the sounds nature and angular position.

Answer 84

Audition: Perception: Speech diaphragm pushes air through vocal chords to create vibration (vibrating sound source) - rate of vibration predicts the fundamental frequency. Vocal tract (resonating chamber - filters) modifies harmonic frequencies - amps frequencies that it vibrates/resonates more to

Answer 85

Audition: Perception: Speech Formant Frequency: are the resonant frequencies of the vocal tract (vibrates more to certain frequencies). Appear as transition to peaks on spectrograms. “Numbered in ascending order- start w/ lowest freq.” Formant transitions: “first 50ms in speech sound” where formant freq smoothly transitions (ba, da and ga all have different transitions)

Answer 86

Audition: Perception: Speech is a different mode of auditory processing required for speech. People who believe in this mode “argue” that this processing is different to non-speech sounds and that speech mode has its own “specialized neural structures”

Answer 87

Audition: Perception: Speech Mode speech processing is qualitatively different because its the only processing that uses categorical perception and is a totally different computation.

Answer 88

Audition: Perception: Speech Mode speech sounds vary by formant frequencies and transitions (like normal sounds vary by freq/pitch) which alters the way the sound is perceived. ‘When altering the transition, the transition becomes more sudden’ - these sudden transitions show sharp boundaries which proves that there are strict phoneme categories Evaluation: speech mode cannot be concluded as categorical perception was the one unique thing to this mode which has been disproven. Differences in speech and nonspeech perception may just be due to us being better “experts” at speech processing since we encounter it so much.

Answer 89

Audition: Perception: Speech Mode smallest unit of sound (e.g. dog = d/o/g)

Answer 90

Audition: Perception: Speech Mode : when a formant frequency reaches a phoneme boundary, the phoneme changes ‘When altering the transition, the transition becomes more sudden’ *some evidence of categorically processing non-speech sounds (e.g. chords) which weakens this argument of qualitative differences

Answer 91

Audition: Perception: Speech Mode Physiological Specialisation in Processing of Speech Sounds: evidence of specialized neural structures Neuropsychology: showed that damage to Wernicke’s Area (in brain’s left hem - posterior temporal lobe overlapping primary and secondary auditory cortex) impaired speech perception (Wernicke's Aphasia) - “may reflect a disturbance in the neural system that links the auditory representation of speech sounds with their meanings.” Neuroimaging: isolate cortex regions that’s activity only reflects speech processing. “used PET to study the brain areas activated solely by intelligible speech” - range of sounds varied by speeches intelligibility, kept acoustic complexity constant. - *left hem preferentially activated in response to speech, intelligible speech = left anterior superior temporal sulcus, non-speech = right hem superior temporal gyrus Two cortical streams of speech processing: Dorsal: left-hem dominant - transforms speech sounds into representations Ventral: “bilaterally organized, and maps acoustic speech input onto conceptual and semantic representations.”

Answer 92

Audition: Perception: Speech Essential component of speech perception - recognition involves categorising “acoustic energies” into “discrete set of meaningful symbols/known words” Becomes more complex as the words meaning depends of the context of consecutive words Characteristics of the speaker alter the pronouncing of the word which further complicates Recent studies show heirarchal processing system using ventral route: primary auditory cortex does initial analysis of speech - midsuperior temporal gyrus forms representations of phonemes and speech formants from “spectral features” - anterior superior temporal gyrus turns “temporal sequence of phonemes” into word representations

Answer 93

Audition: Perception: Speech: Spoken Word Recognition “brains dictionary” - has a representation for each word based on it’s sound (physical properties) and the meaning (symbolic properties).

Answer 94

Audition: Perception: Speech: Spoken Word Recognition prelexical analysis: dividing acoustic signal into phonemes -> potential words are activated to different extends depending on how many features of theirs match the word -> most activated word’s representation is presented and matched to the word

Answer 95

Audition: Perception: Speech: Spoken Word Recognition some argue that recognition only involves bottom-up (words and phonemes are derived only from stimulus info) Others argue that prior knowledge influences early processing - supported by context effects when interpreting incompleted words spoken in a full sentence

Answer 96

Audition: Perception: Auditory Scene Analysis processes that allow people to decompose a complex wave into the individual sounds in order to focus on the correct waves (e.g. focus on the convo while ignoring background noise.

Answer 97

Audition: Perception: Auditory Scene Analysis Auditory Streams refer to the “Grouping of parts of a complex acoustic signal into discrete auditory objects.” discrete auditory objects = sound sources. This grouping is determined by the following physical characteristics: spatial location and spectral content

Answer 98

Audition: Perception: Auditory Scene Analysis ILD’s are only relevant here as ITD’s only work if the sound is previously grouped - therefore cannot be a cue for grouping.

Answer 99

Audition: Perception: Auditory Scene Analysis grouping based on differences in pitch (men have a lower pitch/freq than women). People with different fundamental frequencies allow us to distinguish the two (as fundamental frequency dictates the variation between harmonics (since harmonics are multiples of FF)) based on differences in harmonic series. One stream/melody with alternating high and low pitched notes: splits the tones into two streams (high and low notes) based on two spectral grouping cues: either the shortening of intervals between notes (temporal proximity) or the increased differences of frequency (frequency similarity). Other grouping cues include harmonic similarity (differences based on timbre), amplitude

Answer 100

Audition: Perception: Auditory Scene Analysis sounds spectral components share the same onset and offset - group on the basis of this - the onset and offset differences are perceived as differences in timbre

Answer 101

Audition: Perception: Hearing Dysfunction is caused by issues within the “mechanical structures of the outer and middle ear” - due to damaged T.M., impeded transmission in the ossicles or by blocked ears (with wax or foreign objects)

Answer 102

Audition: Perception: Hearing Dysfunction caused by “damage to neural structures in the cochlea, auditory nerve, or central auditory system.”

Answer 103

Audition: Perception: Hearing Dysfunction: Conductive hole/perforation in eardrum from infection or “violent stimulation”. Results in ‘poorer transmission of sound pressure waves to middle ear’. Further damage to this process comes from scar tissue firming up the membrane. Consequences and Treatment: conduction of sound energy to cochlea is impaired - thresholds increase by 40 - 50 dB for all frequencies: loud sounds heard but muffled. Drugs or mechanical intervention or hearing aid treat these issues: grafts help T.M. if they dont heal, prosthetic ossicles, gromet drains middle ear fluid (but may damage eardrum). Can fully or mostly resolve these issues

Answer 104

Audition: Perception: Hearing Dysfunction: Conductive infection or ostersclerosis (stapes fuses to ossicles) and further scar tissue - restricts movement = restricts transmission of energy. Also caused by the blockage causing fluid build up from middle ear to be drained through eustichan tube into nasal cavity - air cannot flow properly through ossicles (most common cause of conductive hearing loss) Consequences and Treatment: conduction of sound energy to cochlea is impaired - thresholds increase by 40 - 50 dB for all frequencies: loud sounds heard but muffled. Drugs or mechanical intervention or hearing aid treat these issues: grafts help T.M. if they dont heal, prosthetic ossicles, gromet drains middle ear fluid (but may damage eardrum). Can fully or mostly resolve these issues

Answer 105

Audition: Perception: Hearing Dysfunction: Sensorineural Cochlear Damage: Causes: intense sound exposure, ototoxic drug exposure (e.g. antibiotics), infection, metabolic disturbance, allergy, genetic disorders, age (presbycusis). Intense sound exposure e.g.: ruin organ of corti’s elasticity - damaging stereocilia, tectorial membrane, basilar membrane and therefore outer hair cells + transduction. Perceptual consequences of cochlear damage: Raised detection thresholds - sound is de-amplified and distorted (so hearing aid wont resolve distortion) when auditory nerve (freq-tuning) is damaged = outer hair cells lose function and auditory fibers have to broaden their tuning = cannot decompose complex signals Loudness Recruitment: “Abnormally rapid growth in loudness with SPL, resulting from damage to outer hair cells in the cochlea.” hear loud sounds better (why old people say no need to shout) (cochlear damage and outer haircell damage (fibers broadening tuning)) Presbyacusis: can start in 20s, be noticed in 50s, starts to affect high frequencies and slowly goes down the freq spectrum. = due to hair cells deteriorating and losing efficiency’ at base of cochlea first (since base cells respond to all frequencies)

Answer 106

Audition: Perception: Hearing Dysfunction: Sensorineural (auditory nerve damage): “tumours on vestibular nerve can damage auditory nerve” - treatment = surgical removal of tumour = hearing loss

Answer 107

Audition: Perception: Hearing Dysfunction: Sensorineural “hearing issues in noisy environments with no sensory deficits… Treatment is confined to measures that improve the perceptibility of the signal against noisy backgrounds.”

Answer 108

Audition: Perception: Hearing Dysfunction: Sensorineural perception of ringing in head. May persist - debilitating if so. Cause must be in central structures but unsure - one is due to ostesclerosis (refer to the ossicles damage) Isnt classified into either of the groups as origin is unknown. Treatment = in ear sound generators for auditory system, relaxation techniques and CBT to calm down the limbic (emotion) and sympathetic nervous system (arousal).

Answer 109

Audition: Perception: Hearing Dysfunction: Sensorineural treats sensorineural deafness by transducing energy and send to spiral ganglion neurons to take along auditory nerve. Does “information processing of auditory input, reducing dynamic range and bandwidth.” it helps but is not a proper replacement for transduction and encoding processes.

Answer 110

Foureir Theory waveform/collection of sinusodial waves

Answer 111

Physiology: Outer ear cone-shaped eardrum that is located throughout the ear canal. “Air pressure waves cause TM to vibrate” - these vibrations are transferred to the middle ear, through the ossicles and to the cochlea.

Answer 112

the liquid inside the cochlea vibrates, this response is then sent to the brainstem and then the cortex

Answer 113

freq. tuning of auditory nerves is determined by place thats stimulated and displaces in BM - links freq-tuned responses to auditory filters.

Answer 114

techniques include consecutively playing tones with slightly diff freq and participant selects higher freq tone. Discrimination threshold is the amount of freq where participant correctly answers 75% of the time - discrimination is best at lower freq (freq below 1000Hz can discriminate tones w/ less than 1Hz difference. Threshold increases with frequency up to 100HZ (no further) for frequencies above 10kHz (1% change in freq).)

Answer 115

Loudness perception: measurement based on the theory that intensity depends on freq and amp - allows us to examine “the frequency dependence of loudness” - as two waves with different amplitudes can have the same loudness due to frequency. Participant adjusts the frequency of the comparison stimulus until it matches the loudness of the standard stimulus (fixed freq.).

Answer 116

Loudness perception: measurement frequency is coded by the area of the cochlea that experiences max displacement (freq-to-place conversion: (low freq = apical end (wider/flexible), high freq = basal end (narrow/stiff)). Intensity is coded by auditory fibers firing rate. ‘This model explains the link of encoded intensity to loudness perception.’ Equal ratios between auditory nerve’s activity/intensity and perceived loudness. (rate coding) Auditory nerve fibers have different dynamic ranges and characteristic frequencies in order to cover the whole range of human hearing - CF: similar freq require higher intensity to receive same response from fiber Neighbouring neurons waves w/ freq at detection threshold will only receive a response from fibers with that characteristic frequency - neighbouring neurons with similar CF’s fire as intensity increases (as they enter the auditory filters bandwidth of multiple neuron types) - loudness perception increases with the increase of amount of neighboring filters that respond to the same frequency

W4: Audition Flashcards

(140 cards)