PSYC 240 Exam #5

Interaural time/phase differential

-binaural cue for judging azimuth -sound will arrive at the same time if coming from 0 or 180 degrees -sound from the side 600-700 microseconds ITD -brain uses this to locate the sound source -difference is only apparent at the beginning of the sound -only works for low frequency (1 cycle greater than width of head)

Auditory pathway

-cochlear nerve (auditory nerve) -synapse at cochlear nucleus to begin processing -60% of nerve fibers cross over, next stop is superior olivary nucleus (localization) -inferior colliculus (helps with attention and interacts with vision, gets input from superior colliculus -medial geniculate nucleus (by LGN) controls the flow of information to the cortex -auditory receiving area, primary auditory cortex (A1, temporal lobe) - processing for speech, music, etc.

Sound localization

-cues give information about direction and distance of a sound stimulus -cues are either monaural or binaural -two types of directional cues (azimuth - horizontal plane, elevation - vertical plane)

Phase relationships

-depending how you add frequencies (phase starts), you get different sounds -multiple frequencies necessary

Determinants of perceived loudness

-depends intensity but also frequency -not equally sensitive to all frequencies!

Determinants of perceived pitch

-depends on frequency and intensity -fundamental frequency doesn't have to be there, we will still hear it -need combination of 3 harmonics to respond without fundamental -above 5000hz, can't hear a melody

Traveling wave

-displaces basilar membrane close to the base the higher the frequency -lower frequency displaces the membrane nearer to the apex

Outer ear conductive hearing loss

-ear wax: can clog auditory canal -infection of auditory canal (swimmer's ear): swelling reduces diameter of canal -punctured eardrum: sound can't be transduced well

Experience (auditory scene analysis)

-experience influences auditory grouping

Time coding

-frequencies lower than 4000hz can be signaled by the timing of firing -time coding depends on phase locking -groups of neurons work together to signal frequency according to the volley principle -does not work for high frequencies - the precision is not good enough to hit the peaks unambiguously

Audibility function graph

-frequency on X axis, threshold on Y axis (detectability) -above line, you can hear it -human hearing = 20 Hz-20,00 Hz -maximum sensitivity = 2,000-5,000 Hz

Outer ear

-gets sound into the ear -pinna, auditory canal, tympanic membrane (ear drum)

Inner hair cells

-inner hair cells transduce fluid motion into neural signal -1 row of them -3500 per ear -95% of 50,000 auditory neurons synapse at the inner hair cells

Outer hair cells

-inner hair cells transduce fluid motion into neural signal -outer hair cells stretch to amplify and sharpen signal -12,000 per ear

Bending of the cilia

-inner hair cells: fluid from movement of the tectorial membrane over the basilar membrane -outer hair cells: move with the tectorial membrane

Distance cues

-intensity/amplitude/level -frequency -movement parallax -reverberation (echoes)

Function of the outer hair cells

-pressure wave creates fluid movement and basilar membrane is displaced -when basilar membrane is displaced, tectorial membrane moves and displaces cilia of outer hair cells -the hair cells stretch/shrink to sharpen and amplify sound

Conductive hearing loss

-problems getting sound to the hair cells -can be caused by problem in the middle and outer ear

Basilar membrane

-separates the scala tympani and scala media

Riessner's membrane

-separates the scala vestibuli and scala media

Pure tone

-simplest acoustic stimulus -sinusoidal variation in air pressure -one frequency

Superior olivary nucleus

-sound localization -signals from one ear are delayed, the other is not -if signal arrive simultaneously, that intramural time difference has occurred -delay pathway so signas will arrive simultaneously

Location (auditory scene analysis)

-sounds created by a single source usually come from one action in space or move together

Similarity of timbre (auditory scene analysis)

-sounds that have the same timbre come from the same source

Temporal proximity (auditory scene analysis)

-sounds that occur in rapid progression are often produced by the same source

Good continuation (auditory scene analysis)

-sounds that stay constant or change smoothly or group together into a single source

Similarity of pitch (auditory scene analysis)

-sounds with similar frequencies tend to come from the same source

Accuracy of localization

-test by having people point to speaker where pure ton played -less error when low or high frequencies, more when it was a medium frequency -low frequency uses time/phase difference -high frequency uses intensity/level differences -middle frequency uses neither

Spectral cues

-type of monaural cue for judging elevation -how the head and pinnae affect different frequencies depending on the location of the source -pinna has folds, not symmetrical - folds In the pinna affect how the sound hits your ear and your brain can use that to determine where the sound is coming from

Drug effects (hearing loss)

-type of sensorineural hearing loss -caused by nicotine, aspirin, NSAIDS, antibiotics -can effect blood flow or poison auditory nerves

Presbycusis

-type of sensorineural hearing loss -lose ability to hear high frequencies with age

Noise induced hearing loss

-type of sensorineural hearing loss -prolonged exposure to loud noise can damage cilia -ears ringing - recoverable but gets harder every time -caused by smoking or genetics as well

Tinnitus

-type os sensorineural hearing loss -ringing, popping, buzzing, roaring of the ears -temporary: causes by exposure to loud sounds -chronic: caused by prolonged exposure to loud sounds, short exposure to extremely high intensity sounds, or unknown reasons

Meniere's Disease

-type os sensorineural hearing loss -too much endolymph in cochlea and semicircular canals -couses vertigo, tinnitus, vomitting -con come and go - take antidiarhetics to relieve pressure -can destroy vestibular system to eliminate vertigo -typically only on one side

Inner ear

-where sound stimulus is translated into neural signal -osseous labyrinth, cochlea

Interaural intensity/level difference

-works for high frequencies only; low are not effected by head -high frequencies are blocked by the head, creating sound shadow that allows intensity difference -use intensity difference to find location of the sound

Movement parallax (distance cue)

-binaural -the close the source, the more it "shifts" when we move our head

Central pitch processor

- Responds to patterns of harmonics (multiples of frequencies) - Still hear a pitch even if the fundamental isn't there - Needs more than one harmonic - Harmonics: multiples of fundamental frequencies

Equal loudness contour

- curve on graph that all points on the curve are the same perceived loudness

Place coding

-basilar membrane is narrow at stiff at the base, wide and elastic at apex -sound produces a traveling wave of displacement on basilar membrane -frequency of the wave is encoded in the peak displacement (where!) -increasing intensity of a sound increases the amount of displacement (higher amp, higher displacement)

Auditory scene analysis

-auditory grouping principles -how brain figures out what's coming from where and from which sources -if the sounds overlap on the basilar membrane -problem: sounds from different sources are mixed together on the cochlea -location, similarity of timbre, similarity of pitch, temporal proximity, onset/offset, good continuation, experience

Rutherford - early version of time coding

-basilar membrane vibrates as a whole -auditory neurons signal frequency by the firing rate -problem: basilar membrane does not vibrate!

Auditory synaptopathy

-auditory neuron damange -excitotoxicity: neurons are poisons by glutamate, calcium gets in and leads to inhibition in detecting noise among other sounds -poisons structure of auditory nerves

Helmholtz - early theory of vision

-basilar membrane is composed of fiber stretched across -each resonates to a preferred frequency -problem: not stretched - a large area is displaced in response to a single frequency

Cone of confusion

-all points in 3D space that would produce the same ITD and ILD -create same phase and level of difference, can't tell where the sound is coming from

Middle ear

-amplifies and transmits signal to inner ear -ossicles (malleus, incus, stapes), muscles, eustachian tube

Volley principle

-aspect of time coding -look at the firing patter across a set of phase locked neurons -no action potential at every spot for a single neuron, but sum of firing -closer action potentials = higher frequencies -more neurons = higher intensity -all interspike intervals at multiples of the smallest interspike interval

Phase locking

-aspect of time coding -will always fire at or near a particular point -fires at same point in cycle

Muscles (middle ear)

-attached to the malleus and stapes -thought to protect inner ear from high amplitude sounds by contracting

Hearing loss

-legally deaf - can't hear speech sounds at amplitudes less that 82 dB (normal speech = 60 dB) -two types (conductive and sensorineural)

Decibles

-logarithmic scale -represents logarithm of a ration of 2 sound pressure levels -dB of zero does not mean no intensity, it is a sound at the threshold of hearing -danger level = 80 db, prolonged exposure -threshold of pain - 140 dB (jet at take off) -increase of 20db is 10x increase of amplitude -increase of 10db is double of perceived loudness

Evidence for place coding

-masking:one tone can interfere with perception of another tone when they activate the same neurons -tuning curves: each neuron has a characteristic frequency it responds best too that depends on the location (base = lower char. freq, apex = higher char. freq.)

Intensity (amplitude)

-measured in decibel sound pressure level (dB) -how much displacement of air molecules there is (pressure differences between peak and trough) -psychological correlate is loudness

Frequency

-measured in hertz (Hz) -how many cycles/second peak to peak -psychological correlate is pitch (tone height)

Reverberation (distance cue)

-monaural -direct sound (direction to ear) vs indirect sound (reflects off objects) -use ration of indirect/direct to judge distance of source -higher ratio = more distance

Frequency (distance cue)

-monaural -high frequencies are absorbed more by atmosphere -farther sounds are muffled, duller -doppler effect comes into play as well

Intensity (distance cue)

-monaural -the nearer the source, the more intense the sound is -works best for familiar sounds

Complexity of sound

-most sounds are composed of many frequencies -related psychological attribute is timbre -helps differentiate between voices, sounds, etc. -starts with fundamental frequency with harmonics added in

Harmonics

-multiples of fundamental frequencies

Sensorineural hearing loss

-occurs in the middle ear - types: presbycusis, noise induced hearing loss, drugs, tinnitus, meniere's disease

Middle ear conductive hearing loss

-otitis media (ear infection): bacteria travels through- pressure, pain, fluid/puss. Have to drain ear or use antibiotics -otosclerosis: bone overgrowth so the stapes can't vibrate and transmit sound. have to remove stapes and put in prosthetic

Anatomy of the ear

-outer ear -middle ear -inner ear

Envelope of displacement

-part of place coding -the traveling wave never goes above or below a certain displacement level -shows the max displacement at any point on basilar membrane

Organ of Corti

-part of the cochlea -contains hair cells that are responsible for transducing sound stimulus into neural signal -4 rows of hair cells (3 outer, and 1 inner) -outer hair cells embedded

Tectorial membrane

-part of the cochlea -hangs over and moves across the organ of corti -helps the cilia move

Osseous Labyrinth

-part of the inner ear -contains fluid filled chambers -semicircular canals and other structures (vestibular) -cochlea (hearing)

Cochlea

-part of the inner ear -hearing organ -two membranes: oval window (where sound stimulus is transferred) and round window (where pressure is relieved) -3 compartments 1. scala vestibuli (filled with perilymph) 2. scala tympani (filled with perilymph) 3. scala media (cochlear duct filled with endolymph) -scala tympani and media separated by basilar membrane -scala vestiboli and media separated by resigner's membrane -auditory nerve fibers carry information to the brain

Eustachian tube

-part of the middle ear -connects middle ear to back of throat -equalizes pressure between middle ear and outside

Ossicles

-part of the middle ear -made up of malleus, incus, stapes -act as a level to increase force of vibrations and concentrate them -vibrations move to cochlea (used to amplify vibrations to set fluid in cochlea into action)

Auditory canal

-part of the outer ear -conducts sounds to middle ear -helps control climate in middle ear -lined with tiny hairs (cilia) -produces earwax (antibacterial) -amplifies sound

Pinna

-part of the outer ear -funnels sound into the ear -keeps objects out of ear -aids in sound localization

Eardrum (tympanic membrane)

-part of the outer ear -seals off middle ear from outside -mechanical vibrations from pressure variations -vibrates in response to sound

Types of sounds

-periodic sounds: repeating -aperiodic sounds: speech, white noise, etc. -semi-periodic sounds

Psychological attributes of sound

-pitch -loudness -timbre -chroma

Sound

a sound stimulus is created when a source moves or vibrates, causing pressure variation in the air