Hearing Science Final

Basilar Membrane (BM)

A structure in the cochlea that moves in response to sound waves, influencing the bending of stereocilia in hair cells.

Stereocilia

Tiny hair-like structures on hair cells that bend in response to sound vibrations, initiating the process of hearing.

Depolarization

The change in electrical potential across a cell membrane, leading to the generation of a neural signal.

Cochlear Amplifier

A feedback system involving outer hair cells that enhances sound sensitivity and frequency selectivity in the cochlea.

Otoacoustic Emissions (OAE)

Sounds generated within the cochlea, reflecting the active processes of outer hair cells, which can be spontaneous or evoked.

Afferent Fibers

Nerve fibers that carry sensory information from the cochlea to the brain.

Efferent Fibers

Nerve fibers that transmit signals from the brain to the cochlea, modulating auditory processing.

Cochlear Nucleus

The first relay station for auditory information processing in the brainstem.

Superior Olivary Complex (SOC)

A brainstem structure that integrates input from both ears, crucial for sound localization.

Tonotopic Organization

The spatial arrangement of sound frequency processing, where different frequencies are represented in distinct anatomical locations.

Auditory Cortex

The region of the brain responsible for processing auditory information, particularly speech and sound.

Heschel's Gyrus

The primary auditory cortex located in the temporal lobe, crucial for auditory perception.

Wave III of the ABR

An auditory brainstem response wave associated with processing at the level of the cochlear nucleus and SOC.

Wave V of the ABR

An auditory brainstem response wave associated with processing in the lateral lemniscus and inferior colliculus.

threshold

Intensity needed for an individual to just detect the presence of a stimulus. In a clinic the subject has to note hearing the sound 50% of the time it is presented.

minimum audible field (MAF) curve

Plot of threshold as a function of frequency. Measured in sound field, both ears allowed to participate; yields better sensitivity. Measured in free field using loudspeakers. Group averages. People with reported good hearing health

Minimum audible pressure (MAP) curves

Measured under earphones, so one ear at a time. Group averages. People with reported good hearing health.

What matters in measuring threshold for hearing?

• The condition of the individual matters

• The stimulus matters (steady, pulsed, warbled tone)

• How we ask “Can you ____?” matters.

• The environment we test in — matters

• Calibration of equipment matters

• purpose of testing matters ($$)

• Obtained from a neural/physiological response or does client need to signal.

Methods of Limits (most commonly used)

1. Set the frequency - start at 1000 Hz

2. Present a tone - start around 40 dBHL

3. Client responds drop down 10 dB to 30 dBHL

4. Continue dropping by 10 dB steps until the client stops responding

5. Go up in steps of 5dB until client responds

6. Decrease by 10 dB

7. Bracket looking for 2 responses at one level

   Methods of Limits is accurate for clinical purposes, easy to do, and efficient. Ages 4 and up can do this 3 yo can drop a block.

Importance of Instructions

1. You can guess if not sure leads to false positive responses & lower thresholds

2. Wait until you are sure leads to higher thresholds, but fewer false positives

3. Hughson-Westlake (1959) “The purpose of this test is to see how well you can hear some faint tones. Each tone will be quite short. Some will be easy to hear. Others will
   be quite faint. Whenever you hear one of these tones, no matter how faint it is, raise your finger. As soon as the tone goes off, lower your finger.”

   
   

HIT

correctly responding to a tone

Miss

did not respond and tone was there

False positive

subject responds, no tone there

Correct rejection

No response and not tone

Ascending run

Start out below threshold and raise the intensity in steps. Higher thresholds, harder to hear “coming from nothing”. Good if you think someone is malingering as they cannot use your test tone intensity to “set” their response limits. Used by the Veteran’s Administration.

Bekesy audiometry

Client has the controls. Hold the button down as long as you hear it, let up when you do not. Method of adjustment. Not really used clinically. Threshold is the halfway point between peaks on the resulting graph.

Method of Constant Stimuli

Experimental technique, not used clinically. “Constant” number of stimuli are given per intensity per frequency. Randomize order of the intensities presented. Tally how many correct hits happen. Threshold is the intensity at 50% hit rate.

Experimental issues in threshold detection

Noise - breathing, ambient noise, clothing.

Instructions

Age

Guesser

Reward systems

Air Conduction Audiometry

purpose: determine if hearing loss exists and if it does, specify the amount of hearing loss.

The results of air conduction testing give us the degree of hearing loss, but does not tell us the etiology of the hearing loss (i.e., is it conductive, mixed, or sensorineural?)

Audiogram

person’s individual threshold displayed.

“O”

Right ear (red) -air conduction

“X"

Left ear (blue) -air conduction

SF

Sound Field -air conduction

“∆“

Right ear (masked) -air conduction

“⎕“

Left ear (masked) -air conduction

“<“

Right unmasked -bone conduction

“>”

left unmasked -bone conduction

“[“

right masked -bone conduction

“]”

left masked -bone conduction

“┐”

forehead -bone conduction

Normal loss (school aged)

0 - 15 dB HL

Slight (school aged)

16 - 25 dB HL

Normal (adult)

0 - 20 dB HL

Mild

21 - 40 dB HL

Moderate

41 - 55 dB HL

Moderately Severe

56 - 70 dB HL

Severe

71 - 90 dB HL

Profound

91+

visual reinforcement audiometry

For babies starting at 6 - 8 months of age, baby is distracted by distractor, second audiologist plays sound through speaker and baby turns head towards sound and reward stimuli.

flat configuration

hearing loss starts and stops in the same range

Sloping configuration

hearing loss begins better than it ends

Rising configuration

hearing loss is worse and then rises to better

High Frequency

can be used instead of sloping, when a HL is just in the high pitches

Low frequency configuration

used interchangeably with rising

cookie bite configuration

when the hearing loss is normal at both ends and the loss is in the mid pitches only

Interpretation of results

Normal hearing

hear is within normal hearing limits

Conductive hearing loss

(CHL) hearing loss is within the outer or middle ear - when there is a loss in air conduction but not bone conduction

Sensorineural hearing loss

(SNHL) there is a hearing loss in bone conduction as well, bone and air conduction are the same loss

Mixed hearing loss

There is a bone conduction hearing loss and a worst loss with air conduction as well.

peripheral auditory system

external ear (pinna, external auditory meatus)

middle ear (tympanic membrane, ossicles, middle ear cavity)

inner ear (cochlea and vestibular system)

Auditory nerve (VIIIth Cranial nerve)

Central auditory system

auditory nerve

parts of the brain (cochlear nucleus, superior olivary complex, lateral lemniscus, inferior colliculus, medial geniculate body, and cortex)

middle ear

sound conduction into the inner ear with minimal loss due to impedance mismatch

External ear

sound conduction into the middle ear

localization

Inner ear

transduction of sound from mechanical input to neural output

Auditory nerve

carrying the neural impulse to the brain

Air conduction (AC)

transmission through outer, middle, inner ear, and higher up.

sounds presented by headphones, insert earphones, loudspeakers

Bone conduction (BC)

Transmission that stimulates the inner ear directly through mechanical vibration of the skull

Sounds presented through a bone vibrator

Temporary

true TTS is due to damage from loud sounds. K+ does not have time to leave the cell-swelling

Permanent

Destruction of hair cells or basilar membrane, chronic or acute noise exposure. NIHL.

Hearing losses, bone vs air

Place of articulation, manner of articulation, and voicing

Vowel Quadrilateral

Dipthongs

Anterior/Ventral

In front, toward face

posterior/dorsal

behind toward the back of the head

Lateral

toward the side of the head

medial

toward middle of head

superior

above toward top of head

inferior

below toward the feet

cranial/cephalic

toward the head

caudal

toward the tail

Outer Ear

Conductive - Pinna, EAM (external auditory meatus), Tympanic membrane

Middle Ear

Conductive - TM, ossicles (malleus, incus, and stapes), and ligaments and muscles

Inner Ear

Sensorineural mechanism - Vestibular Apparatus, cochlea (basilar membrane and organ of corti), and auditory nerve

Conductive Loss

problem with the outer and/or middle ear

sensory

issue is in the cochlea

neural

issue is in the VIIIth cranial nerve

Sensorineural

issue with the cochlea and/or VIIIth nerve

Mixed

conductive and sensorineural both involved

central loss

central auditory system dysfunction

Temporal Bone

Encases most of peripheral auditory structures except cartilaginous part of the external ear and the short portion of the auditory-vestibular nerve between the opening of the internal auditory meatus and the brainstem -complexly shaped. Protects inner ear structures, contains two important openings: external and internal auditory meatuses.

4 portions: squamous, petrous, mastoid, and tympanic

Squamous - Temporal Bone

Protects the temporal lobe of the brain

Petrous - Temporal Bone

Floor of the cranium, very hard, thick, protective, surrounds the inner ear (balance and hearing)

Mastoid - Temporal Bone

air filled (honeycomb, strong and light). Upper front par - tympanic antrum is air filled and lined by prolongation of the mucous membrane of the tympanic cavity. Tympanic antrum bound above by the tegmen tympani which separates it from the middle fossa of the base of the skull; below by the mastoid process; laterally by the squama just below the temporal line and medially by the lateral semicircular canal of the internal ear which projects into its cavity. It opens in front into that portion of the tympanic cavity which is known as the attic or epitympanic recess.

Mastoiditis

Infection of the mastoid. Sequela of untreated middle ear infections. bacterial in nature. Chronic or acute in nature, and can result in removal of the bone.

Tympanic - Temporal bone

The base and walls of the middle ear space

Pinna or Auricle

Poorly innervated, very variable, vestigial muscles, 4 dB increase in sound level, minimal localization. Structures are composed of cartilage; the cartilage continues part way into the external auditory meatus. Structures of the pinna play a role in localizing enviro sounds in the up-down and front-back dimensions and high pitch sounds from back of the hear.

Funnels sound into ear. Has a resonance around 5000-6000 Hz. Blocks high frequency sounds that are coming from behind the ear.