Hearing Science

Place coding

tonotopic organization in every nucleus and across the auditory nerve

Cranial nerves related to the CANS

8, 5, 3, 4, 6, 10, 7

Cranial nerve 8

Vestibulocochlear nerve, provides hearing and balance information

Cranial nerve 5

Trigeminal, sensory innervation to tympanic membrane and motor information to tensor tympani

Cranial nerves 8,4,6

oculomotor, trochlear, and abducens, control eye movement

Cranial nerve 10

vagas, sensory information to outer ear and tympanic membrane

cranial nerve 7

facial, sensory information to stapedius

Temporal coding

How sound is represented using timing of neural firing, where they fire convey information

4 temporal coding firing patterns

primary-like, chopper, pauser, and onset

Primary-like

cells produce signals that are similar to the signal in the auditory nerve

chopper cells

cells fire periodically but the period of their response doesn’t match the period of the stimulus

pauser cells

fire in response to the onset of a stimulus, but then they take a break then fire at a lower level

onset cells

fire only at the onset of the stimulus

Bushy cells location

AVCN

Bushy cells

only a few neurons connected to each cells, have a narrow range of frequencies

Octopus cells location

PVCN

Octopus cells

many neurons connect to each cell, responds to a wide range of freuqencies

Binaural hearing is important for

sound localization, distance estimation, and understanding of speech

Factors localization depends on

time and intensity

What factor for localization with low frequencies

intra-aural time difference

What factor for localization with high frequencies

intra-aural intensity difference

Right ear advantage

People understand speech better when directed towards right ear because it is connected to the left ear

Sensation

awareness of a stimulus

perception

recognition and interpretation of a stimulus

hearing

awareness of a sound

listening

couscous effort to hear a sound

Reasons for variability in human responses to auditory stimuli

instruction, bias, anticipation, external and internal noise, attention, motivation, training, and others

Intensity is perceived as

loudness

Frequency is perceived as

pitch

duration is perceived as

duration change

spectral complexity is perceived as

timber change

absolute threshold

minimum value of a stimulus that results in a reaction

terminal threshold

maximum value of a stimulus before a sound is painful

difference threshold

smallest difference a listener can notice

Response bias

a person responds in a specific way because of expectations, experience, or psychological factors

Hit

when a signal is presented and responded to

miss

when a signal is presented but not responded to

false alarm

when a signal is not presented but is responded to

correct rejection

when a signal is not presented and is not responded to

Difference limen

smallest decectable difference between two things

Method of Limits

Used in audiology. Sound is increased or decreased until a threshold is met. Time effective and reliable

Upper limit of frequency

threshold of feeling/pain

Lower limit of frequency

threshold of hearingq

Sound heard

20-20,000

Most sensitive area of hearing

300-500 Hz, where speech is

frequency heard

0-120 dB SPL

Masking principles

greatest when frequency is close to signal frequency, low frequency signals mask high frequencies better, greater masker intensity-greater shift (louder noise harder to hear), ear generates harmonic distortions at high intensity

Why is timbre important

allows you to hear difference between sounds at same frequency and duration

advantages of binaural hearing

improves sound quality, speech intelligibility in noise, localization, spacial orientation

cues that assist with localization

binaural and monoaural

binaural cues

both ears, help figure out which side a sound is coming from

monoaural cues

individual ears, if sound is coming from front, back, up, or down

decasate

crossing over

what does tonotopic organization is maintained throughout the CANS mean

in cochlea, auditory nerve, and each nuclei, in entire system

Loudness unit

phon

pitch unit

mel

intensity

dB SPL, quantifiable, measurable

lousness

description, super loud, very quiet

frequency

in Hz

pitch

description, very low

how do you hear your own voice

bone conduction

why do you get dizzy when you stop spinning

lag of hair cell response, body thinks you’re still spinning

Organ of corti is in the

scala media

vibration of the skull bones results in hearing via

bone conduction

cone shaped membrane that is attached to the malleus

tympanic membrane

outer portion of hear, sticks out from head

pinnia

seen on anterior inferior quadrant of eardrum

cone of light

portion of the ear responsible for mechanical energy

middle ear

air filled cavity with three small bones

tympanic cavity

middle ear bones are called

ossicles

scala media is filled with

endolymph

hair cells have _____ projecting from one end

stereocilia

_____ motion of the stereocilia makes them bend and lets K+ in

shearing

air pressure in the tympanic cavity is maintained by

eustachian tube

the _____- twists 2 and ¾ times

cochlea

tallest tips of the outer hair cells touch the

tectorial membrane

scala vestibuli and scala tympani are filled with

perilymph

mapping stimulus frequency to place on the basilar membrane is called _____ theory

place

this ossicle attaches to the oval window

stapes

the ____ theory states the cochlea transmits frequency information based on the rate of neural impulses

periodicity

determining the location of a sound source

localization

s shaped and ends in the tympanic membrane

ear canal

the _____ is the size of a peanut M & M

inner ear

the ear canal’s natueal resonance is around

3000 Hz

the acoustic reflex occurs in response to ___ sounds

loud

Ear canal length

2.5 cm

Effective acoustic length of ear canal

25% longer because of end effect

outer 1/3 of ear canal

cartilaginous portion

inner 2/3 of ear canal

bony portion, no hair or glands

outer ear functions

transmission, direction, and protection

Middle ear protection

narrow, curvey, hair traps outside cells, ear wax protects

Tympanic membrane is held by

annulus ligament

parts of tympanic membrane

pars tensa and pars flaccida

layers of tympanic membrane

outer (continuous with ear canal), middle (fibrous tissue), and inner (mucous membrane)

ossicles

malleus, incus, stapes

antrum

small chamber in mastoid portion of temporal bone

otoscopic examination

views the middle ear through the tympanic membrane

transducer

device that changes energy

middle ear energy change

acoustic sound to mechanic energy

ossicular level

pressure in the incus is 1.5 times greater than the pressure in the malleus because it is longer