chapter 9-physiology and psychoacoustics Flashcards by Megan miller

sound waves consist of what

pressure waves carried by vibrating air molecules

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how fast do pressure waves move through air

how fast through water

335 meters per second

5x faster through water

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compressions

parts of the wave where air pressure is increased

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rarefractions

parts of the wave where air pressure is decreased

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does sound travel through space

yes, but we can’t hear it

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sound is created when

objects vibrate and pressure changes in the medium

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the simplest sound is a ___ wave, and has __ important properties

sine, 3

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frequency

corresponding to the number of compression/rarefaction cycles per second, measured in hertz (Hz)
fine details with aspects of sound

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hertz

Hz; cycles per second (cycles/second=Hz)

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auditory range

20 Hz-20,000Hz

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amplitude

corresponding to the amount of change in pressure, measured in decibel (dB) sound pressure level (SPL); magnitude of displacement of a sound pressure wave

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decibels

dB; how we actually hear sounds; relative measure, relations to thresholds, logarithmic scale (logx where x=amplitude (physical)/threshold amplitude

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sound pressure level

SPL; in relation to threshold at 1000Hz->dB=0

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can decibels be positive or negative

yes

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phase

corresponding to the part of the cycle that a wave has reached at a given point in time, measured in degrees (0-360)

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human hearing used a limited range of frequencies (__) and sound pressure levels (__)

Hz, dB

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sine waves are not common in everyday sounds because not many vibrations are ___

pure

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most sounds are ___

complex

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complex sounds are best described as a ___ that displays how much ___ is present in each of the ___ in the sound

spectrum, energy, frequencies

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complex sounds ___ across frequencies

combine

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sine waves/___ tone

pure; wave form for which variation as a function of time is a sine function

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spectrum

representation of the relative energy present at each frequency

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sounds are first collected from the environment by the ___ in the __ __

pinnae; outer ear

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pinna

outer, funnel-like part of the ear; flexible flap on the outside

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sound waves are funneled by the pinna into and through the ear canal, which ___ sound frequencies between 2000 and ___ HZ, and protects tympanic membrane from damang

enhance; 6000

outer ear

pinna; focuses sound waves onto the entrance of the ear canal

shape and size of outer ear

amplify medium (band pass: 1500-7000Hz) sound frequencies and attenuate (reduce) high frequencies

what physically moves the eardrum (tympanic membrane)

sound waves

middle ear

physically transmits sound energy from the eardrum to the oval window in the inner ear

small bones ___ the force received from the ear drum and concentrate it onto a small area of the oval window

amplify; middle ear

to reduce loud sounds, the inner ear uses what muscle

the tensor temporal muscle

acoustic reflex of the middle ear

protects ear from intense sounds; takes ~20ms

what amplifies sounds in the middle ear

bones

what attenuates sounds in the middle ear

muscles, ear drum, stapedius

3 bones in the inner ear

malleus, incus, stapes

inner ear

fine changes in sound pressure are translated into neural signals; transduction

function of the inner ear

roughly analogous to that of the retina

cochlea

part of the inner ear where auditory transduction takes place

hair cells

cells that support the stereocilia which transduce mechanical movement in the cochlea into neural activity sent to the brain stem (afferent)

some hair cells also receive input from the brain

efferent

how do hair cells cause changes in signaling to get transduction to occur

physically move

1 inner hair cell goes to many afferent fibers

divergence

more outer hair cells (3x more)

3500 inner, 10500 outer

inner hair cells are

afferent, sensory

outer hair cells are

efferent, motor feedback

basilar membrane

plate of fibers that forms the base of the cochlear partition and separates the middle and tympanic canals in the cochlea

cochlear partition

transduction of sound waves into neural signals

inner hair cells; fluid displacement

deflects the stereocilia of inner hair cells, resulting in graded potentials (not action potentials)

the base of each inner hair cell makes contact with __ fibers of the auditory nerve

afferent; divergence

stereocilia

hairlike extensions on the tips of hair cells in the cochlea that initiate the release of neurotransmitters when they bend; mechanoreceptors

simplified cross section through a ___ cochlea

uncoiled; moving fluid

oval window is where __

fluid starts

apex is the _____

farthest away; loose and wide

base

stiff and thin

travelling wave component

fluid/pressure displacement; standing wave; location of displacement for given frequency

inner ear; frequency to place conversion

basilar membrane vibration at different sound frequencies

coding of amplitude and frequency in the cochlea: place code

tuning of different parts of the cochlea to different frequencies, in which info about the particular frequency of an incoming sound wave is coded by the place along the cochlear partition with the greatest mechanical displacement

the auditory nerve (AN)

responses of individual AN fibers to different frequencies are related to their place along the cochlear partition; hair cells connect to AN

frequency selectivity

clearest when sounds are faint

different AN fibers have different

thresholds

rate saturation

the point at which a nerve fiber is firing as rapidly as possible and further stimulation is incapable to increasing the firing rate

isointentisty curves

a chart measuring an AN fibers firing rate to a wide range of frequencies, all presented at the same intensity level

rate intensity function

a map plotting firing rate of an auditory nerve fiber in response to a sound of constant frequency at increasing intensities

psychoacoustics

the study of psychological correlates of the physical dimensions of acoustics

intensity and loudness; audibility threshold

a map of just barely audible tones of varying frequencies (like contrast sensitivity function); more sensitive to mid range frequencies; lowest sound pressure level that can be reliably detected at a given frequency

intensity and loudness; equal loudness curve

graph plotting sound pressure level (dB SPL) against the frequency for which a listener perceives constant loudness

hearing aid

amplifies sound through the middle ear

cochlear implant

electrically stimulate the inner ear, bypassing the outer and middle ear; directly stimulate auditory nerve fibers

pitch

of times per second that a pattern of pressure change repeats; frequency