Exam 1 Audiology

Audiology

Discipline that focuses on the assessment and treatment of hearing (auditory) and balance (vestibular) disorders

Two main professional organizations for audiologists

American Academy of Audiology (AAA) and American Speech Language Hearing Association) (ASHA)

How and when did audiology as a profession first begin?

Created around World War 2 with returning veterans with hearing loss. Civilian Sector Expansion largely staffed by SLPs, diagnostic focus, hearing aid dispensing and diversification

Father of Audiology

Raymond Carhart, taught at Northwestern

Academic/ clinical requirements that are needed to become an audiologist

Entry level degree is Doctor of Audiology (AuD), which is 3 to 4 year graduate degree.

Legal Requirement to become an audiologist

State license

Medical Audiology

Primary concern is determining site and cause of hearing problem. Employed in hospitals

Educational Audiologist

Serves children in schools, usually employed by a contractor

Pediatric Audiology

Concentration on the audiologic management of children

Dispensing Audiologist (rehabilitative)

Fous is typically on management of anyone with hearing impairments. works in a private practice, as part of a rehab group or with ENT

Industrial Audiologist

Concerned with noise measurements, develop programs protecting employees from noise exposure, assisting with guidelines

University/ Research

Academic position, teaching

Recreational Audiology

Practice of hearing conversation and consumer education regarding products and services used to enhance and preserve hearing occupations

Animal Audiology

Study of assessment and management of hearing loss in animals

How is sound produced

Sound production requires a vibrating source and a medium that is capable of being set into vibration of sound

What are sounds

Pressure waves with alternating higher and lower pressure regions that move through the medium

Positive Pressure

Higher, compression: air molecules bunched up

Negative Pressure

Lower, rarefaction, air molecules spread out

Why does the tympanic membrane move in and out

It converts sound waves into physical vibrations that brains can translate. Due to pocket of air in ear.

Sound Propagation; Reflection

When a sound (from air) encounters an obstacle with relatively high density (greater impedance, water) some reflection of the sound wave can occur

Frequency

The number of cycles (of vibration) per second. Measured in Hertz. Healthy human ear is sensitive to frequencies between 20 and 20,000 Hz.

Period

Total time it takes for one full wave cycle to pass a single point

Amplitude

Extent of Vibratory Movement of a mass from its position of rest to that point farthest from the position of rest. General term for magnitude, measured in units of intensity and pressure

Phase

Where a sine wave starts at some arbitrary time, measured in degree or radian. Important for summation of signals, active noise cancellation audio devices

Intensity

The amount of sound energy that passes through a particular area in one second

Pressure

The amount of force that is applied by the moving molecule per unit area

Decibel

Unit of measurement of sound amplitude (magnitude/intensity/ pressure) used in acoustics and in audiology

Why dB

Sounds are pressure waves. Sound amplitude can be measured as pressure (Pa or µPa). However, range humans can hear is very large so dB scale had to be invented.

dB SPL

Used in sound level meters to quantify magnitude of sound in acoustic measurements. 0 dB SPL means the pressure of measure signal is the same as reference, doesn’t mean no sound.

Positive values of dB SPL

Means sound pressure is greater than the reference

dB HL

Used in audiometers, key in audiology, 0 dB HL means same as normal hearing threshold. reference is normal hearing threshold (lowest level listeners can barely hear)

Positive dB HL

greater amplitude than normal hearing threshold

dB SPL or HL

dB SPL or HL cannot be added or subtracted directly due to the log scale of dB SPL

Simple and Complex Sounds

Very few naturally-occuring pure tones (sinewaves). most sounds are complex and contain energy from different frequencies, amplitudes and phase relationships

Speech Banana

Term used to describe the area where the phonemes, or sounds of human speech, appear on an audiogram

Audiogram

Graph showing the results of a pure-tone hearing test. Shows how loud sounds need to be at different frequencies for you to hear them.

Signal-to-Noise- Ratio

The level of a desired signal to the level of background noise. (Desired noise 75 minus background level 68) = +7 dB

Five major components of the auditory System

EE, ME, CO, AN, Central Auditory Nervous System

EE

External (Outer) Ear: Conducts sound from the environment to the middle ear and modify (amplify) the acoustic properties of those incoming sounds

ME

Middle ear, converts the acoustic energy from the outer ear to mechanical energy via tympanic membrane, and then pass it on through the ossicular chain to the inner ear. Also amplify the sounds

CO

Cochlea (inner ear) Convert the mechanical energy into electrical impulses that the brain can interpret

AN

Auditory Nerve, carry the electrical impulses to the central auditory nervous system for further processing and interpretation

Central auditory nervous system

Further processing of sounds and interpretation of the sounds

What structures constitute the peripheral auditory system

Auditory Nerve, cochlea, middle ear, and external ear

Organ of hearing

Organ of corti

How is sound frequency encoded in the cochlea

Frequency= location of maximum of the basilar membrane. Low frequencies- toward the apex. high frequencies- toward the base.

What auditory structures make up the conductive mechanism

Middle ear and external ear

What auditory structures make up the sensory/ neural mechanism?

Central auditory nervous system, auditory nerve, and cochlea (inner ear)

What is the air conduction pathway

Air conduction tests. any sound that courses through the outer ear, middle ear, inner ear, and beyond is heard by air conduction. hearing by air conduction depends on the functioning of the outer, middle, and inner ear and of neural pathways beyond

Bone conduction pathway

bone conduction tests- bypass the outer and middle ear by vibrating the skull mechanically and stimulating the inner ear directly. hearing by bone conduction depends on the functioning of the inner ear and beyond

What is an audiogram

What is the type of transducer for AC testing?

Insert earphones, supra-aural earphones, circumaural earphones, loudspeakers

What is the type of transducer for BC testing?

bone conduction vibrator

What is the definition of pure-tone threshold

The lowest intensity level the patient responds to at least 50% of a series of ascending presentations, with at least two responses out of at least three trials (max 4) for a single level. use a transducer to obtain

What is the ‘up-5-down-10” procedure- AKA modified Hughson-Westlake

Increase level 5 dB when patient does not hear. Decrease level 10dB when patient hears

what frequencies does routine AC testing include

250 Hz through 8000 Hz. 125 may be tested and so can 20,000

Sound Pressure Level

dB SPL= 20 x log (pressure/standard reference pressure)

standard reference pressure

20 μPa

1 Pa

1,000,000 micropascals μPa

Major landmarks of pinna

Helix, earlobe/lobule, tragus, antitragus, concha

Which portion is cartilaginous

External ear, lateral 1/3 canal

which portion produces cerumen

external ear

which portion is bony

cochlea

Ossicles

form the connection between the TM and inner ear. malleus, incus, stapes

inner hair cells

1 row of 3,000 hair cells

outer hair cells

3-5 parallel rows of 12,000 to 15,000 hair cells

anotia/microtia

external issue, can occur alone, with other birth defects, or as part of a syndrome

atresia

Birth defect. Baby born without fully developed ear canal

impacted cerumen

Solid buildup of earwax that blocks ear canal and causes discomfort/ hearing problems

otitis externa

aka swimmers ear. infection/ inflammation of the ear canal

otosclerosis

abnormal bone remodeling condition in the middle ear that fixes the stapes bones in place, causing progressive hearing loss

noise-induced hearing loss

can be caused by sounds measuring 85 decibels or higher

hearing loss due to aging

presbycusis

acoustic neuroma (vestibular schwannoma)

slow-growing, noncancerous tumor that develops on the main nerve leading from inner ear to the brain

Ménière’s disease

chronic disorder causing sudden attacks of vertigo, fluctuating hear loss, tinnitus, and feeling of pressure or fullness

air conduction pathway

conductive portion and sensory/neural portion

bone conduction pathway

sensory/ neural portion

conductive portion

outer ear and middle ear

sensory/ neural portion

inner ear, CN VIII, central system