chapter 9-physiology and psychoacoustics Flashcards
sound waves consist of what
pressure waves carried by vibrating air molecules
how fast do pressure waves move through air
how fast through water
335 meters per second
5x faster through water
compressions
parts of the wave where air pressure is increased
rarefractions
parts of the wave where air pressure is decreased
does sound travel through space
yes, but we can’t hear it
sound is created when
objects vibrate and pressure changes in the medium
the simplest sound is a ___ wave, and has __ important properties
sine, 3
frequency
corresponding to the number of compression/rarefaction cycles per second, measured in hertz (Hz)
fine details with aspects of sound
hertz
Hz; cycles per second (cycles/second=Hz)
auditory range
20 Hz-20,000Hz
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
decibels
dB; how we actually hear sounds; relative measure, relations to thresholds, logarithmic scale (logx where x=amplitude (physical)/threshold amplitude
sound pressure level
SPL; in relation to threshold at 1000Hz->dB=0
can decibels be positive or negative
yes
phase
corresponding to the part of the cycle that a wave has reached at a given point in time, measured in degrees (0-360)
human hearing used a limited range of frequencies (__) and sound pressure levels (__)
Hz, dB
sine waves are not common in everyday sounds because not many vibrations are ___
pure
most sounds are ___
complex
complex sounds are best described as a ___ that displays how much ___ is present in each of the ___ in the sound
spectrum, energy, frequencies
complex sounds ___ across frequencies
combine
sine waves/___ tone
pure; wave form for which variation as a function of time is a sine function
spectrum
representation of the relative energy present at each frequency
sounds are first collected from the environment by the ___ in the __ __
pinnae; outer ear
pinna
outer, funnel-like part of the ear; flexible flap on the outside
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
