Glossary of Audiology Terms
Acoustic Meatus: Another name for the external
ear canal through which sound travels from the concha of the pinna to the
Acoustic Nerve: The vestibulocochlear nerve or
the auditory nerve. The VIIIth cranial nerve which runs from the inner ear to
the brainstem and contains fibers carrying both auditory and vestibular
Acuity: In hearing terms, it refers to the
clarity or audibility of sound.
Aditus – opening between the pneumaticized mastoid air
cells and the middle ear space
AD: Right ear.
Air-Conduction Thresholds: The lowest level
that an individual can hear a pure tone stimulus presented through headphones or
insert earphones. During a hearing test a patient's air-conduction thresholds
are measured at several frequencies associated with the normal pitch range of
the human voice and graphed out onto an audiogram.
American Academy of Audiology – Largest of the
professional organizations for audiologists.
American Speech-Language Hearing Association –
Professional organization for both speech-language pathologists and
Amplifier: An electronic sound processor
located inside of a hearing aid that increases the incoming signal to improve
the audibility of the outgoing signal.
Ampulla – the enlarged section of the
semicircular canal in which the sense organ for head rotation is located.
Anatomy – the study of the structures of the
Antagonistic – pulling in opposite directions.
The contraction of the stapedial muscle and tensor tympani are antagonistic.
Antihelix – part of the pinna that is just
beyond the concha; it is a rim of cartilage.
Arch of Corti – also called pillars of Corti.
Supporting structure located between the inner and outer hair cells within
the organ of Corti.
Areal ratio – the relative difference in the
size of the tympanic membrane to the stapes footplate. Because of this
size difference, sound is concentrated as it reaches the inner ear, and the
sound pressure is enhanced by about 27 dB.
Anacusis: Absence of sound. Deafness.
AS: Left ear.
Assistive Listening Devices (Alds):
Non-hearing aid devices used by a hearing impaired individual to improve
communication and the performance of activities in specific environments. ALDs
include devices such as infrared and FM personal amplifiers, alerting devices,
and closed captioning equipment.
Atresia: The absence or closure of the
external auditory meatus (ear canal).
Au.D.: Doctor of Audiology. A clinical
Audiogram: A chart onto which is graphed the
results of a hearing test. The chart has intensity levels listed on one axis and
frequencies (pitches) listed on the other axis.
Audiology – the science of the assessment and
management of hearing and balance disorders.
Audiometer: The electronic piece of equipment
employed by a hearing healthcare professional to assess the hearing thresholds
and speech awareness / processing ability of an individual.
Audiometric Evaluation Or Audiometry: Another
name for a hearing test or hearing evaluation.
Audiologist: A hearing healthcare professional
who has earned a Masters Degree (M.S. or M.A.) or Doctorate Degree (Au.D. or
Ph.D.) in audiology or a related field of study. Some activities that
audiologists are involved with are the assessment and treatment of hearing and
vestibular disorders, the dispensing of hearing aids, research, industrial
consultation, and/or teaching.
Auditory Brainstem Response (ABR) Testing:
Also know as Brainstem Auditory Evoked Response (BAER) testing and Auditory
Evoked Response testing. A test requiring specialized equipment that measures
the electrical activity in the brainstem after the presentation of a signal. The
test is utilized in the threshold assessment of hard-to-test individuals and to
evaluate the integrity of the brainstem pathways.
Aural Rehabilitation: Therapy or training
sessions designed to improve communication skills.
Auricle: The pinna. The cartilaginous
structures of the external ear located peripheral to the skull.
Axon – portion of a neuron than conveys the
neural impulse away from the cell body to the terminal button.
Basilar membrane – membrane inside the cochlea
that separates scala media and scala tympani; on this membrane rests the
organ of Corti.
Brainstem – portion of the brain that is below
the cerebrum and anterior to the cerebellum. It is a conduit of
information to the “brain” and to the cerebellum (the cerebellum coordinates
Behavioral Audiometry: A hearing test that
requires some type of visible and voluntary response from the individual being
Behind-The-Ear Hearing Aid: A style of hearing
aid in which the electronic portion of the hearing aid (including battery,
microphone, speaker, amplifier, etc.) is located on top of or behind the ear.
The electronic portion is connected via a piece of tubing to an earmold, which
is in the ear.
Bilateral: A term used to signify that both
ears or both sides of the head are involved (i.e., He has bilateral
Binaural: Refers to when sound is presented to
both ears (i.e., She wears binaural amplification.).
Binaural Advantages: The benefits derived by
the average patient, with equal or fairly equal hearing loss, from the use of
hearing aids on both sides. Including:
Binaural Summation: an increase in
intensity of a sound of 3 to 9 dB when hearing the sound through both ears
compared to just one.
Binaural Squelch: the improved
ability to focus on a desired sound in the presence of undesired sounds when you
hear it through both ears.
Localization: the ability to determine
the location of the source of a sound.
Head Shadow: a decrease in the head
shadow effect is another advantage of binaural amplification.
Blocked Or Inflamed Eustachian Tube:
Eustachian tube dysfunction. A condition in which the tube that connects the
throat and middle ear cavity is not allowed to open and close as it would in a
normal ear system for the purpose of pressure equalization. When the eustachian
tube becomes blocked or inflamed it will not allow a person to "pop" their ears
and can lead to negative pressure, fluid in ear, and/or middle ear infections.
Body Hearing Aid: An older style of hearing
aid in which the electronic components and batteries are located in a single
casing located on the body, away from the ear. The device is connected to the
earmold via a wire. Body worn aids are generally used to provide amplification
for individuals with profound hearing losses.
Bone-Conduction Thresholds: The lowest level
that an individual can hear a pure-tone stimulus presented through a vibrator
placed on the mastoid bone or forehead. Bone-conduction threshold testing
attempts to assess the ability of the sensory and neural auditory systems
without the sound passing through the outer and middle ear.
Calibration: The regular tuning of an
audiometer to set the presentation values at levels consistent with
Cartilaginous – comprised of cartilage, a dense
but flexible connective tissue.
Cerebellopontine angle – area where the VIII
nerve enters the brainstem. At this location, the auditory pathway
takes a turn (angles) upward. This occurs at the junction of the
cerebellum and pons portion of the brainstem, ergo the name.
Central Auditory Processing: The awareness of
an auditory signal in the central nervous system, that occurs beyond the
peripheral auditory system (outer ear, middle ear, and cochlea), and the
interpretation / processing of that signal.
Cholesteatoma: A benign expanding mass which
can form in the middle ear cavity. It is made up of skin and cholesterol
crystals. The mass can become infected and cause other problems in the middle
Cilia – tiny hairlike projections on a cell.
Ciliated cells are found in portions of the middle ear space, the Eustachian
tube, and in the cochlea. Cilia are found on both outer and inner hair
Circuit Noise: Extraneous sounds present in
the output of a hearing aid that are related to the function of the hearing
aid's mechanism, not due to external sounds.
Clinical Audiologist: An audiologist who
specializes in the assessment, treatment, and rehabilitation of hearing and
Closed Captioning: The transcription of oral
words and sounds, present in a TV or movie broadcast, into written words and
displayed for the purpose of improving a hearing impaired individual's access to
Cochlea: The snail-shaped portion of the inner
ear that contains the hair cells and nerve endings that convert a sound from the
mechanical/vibratory movements present in the middle ear into an electrical
charge, as the sound travels to the brain for processing.
Cochlear nucleus – Group of nerve cells just medial to
the VIII nerve. The first nucleus in the auditory pathway.
Cochlear Implant: An electronic device, a
portion of which is surgically implanted into the inner ear, that is designed to
provide a sensation of sound to deaf individuals.
Communication Disorder: Any abnormality in
speech, language, or hearing processes that results in an inefficient exchange
Completely-In-The-Canal (CIC) Hearing Aid: A
hearing aid that is designed so that most of the electronics are located in the
ear canal. The smallest style of hearing aid currently available.
Compression: An internal feature present in
most current hearing aids that helps to control the intensity of higher volumes.
There are many varieties of compression and each one has its advantages and
disadvantages, but they all in someway make the hearing aid non-linear.
Concha: The bowl area of the pinna (auricle)
that channels sound from the environment to the ear canal.
Condensation – also called compression. The
portion of a sound wave where the air molecules are most tightly packed
together. See also the tutorial on acoustic review.
Conditioned Play Audiometry: A method utilized
in the assessment of hearing abilities of pediatric patients. The child is
trained to perform a specific enjoyable task whenever a sound is presented.
Conductive Hearing Loss: A decrease in an
individual's ability to hear a particular sound due to an inefficiency or
disruption in the outer ear or middle ear system. A conductive hearing loss is
when the sounds are somehow "blocked" as they travel from the pinna to the
Cone Of Light: A triangular brightness visible
on the lower portion of the tympanic membrane (eardrum) during otoscopy due to a
reflection of the light coming out of the otoscope.
Congenital Hearing Loss: The presence of
hearing loss at or before birth.
Cookie Bite Audiogram: A description of the
graph of an individual's hearing thresholds in which the middle frequencies are
noticeably poorer than the low and high frequencies.
Cortex – outside portion of the cerebrum,
consisting of gray matter (material that is mostly cell bodies, rather than
white matter, which is mostly myelinated neurons).
Crus – singular (crura is plura), from the Latin
word meaning leg, it is a side part of the stapes bone of the middle ear.
CROS Hearing Aid (Contralteral Routing Of Signal):
A type of hearing aid designed for individuals with unilateral hearing loss
which picks up the sound on the impaired side of the head and delivers it to the
normal or near normal hearing ear.
Cued Speech: Various hand shapes utilized by
someone who is speaking to a deaf individual to enhance the speech reading
Custom Hearing Aid: A hearing aid fashioned in
its size and amount of amplification to appropriately match a specific patient's
dB HL – decibels hearing level. 0 dB HL is
the softest sound that can be heard by the average person with normal
hearing. It is not the absence of sound, as persons with better than
average hearing will have thresholds lower than 0 dB HL (e.g. –10 dB HL).
dB SL – decibels sensation level. The
number of decibels above another threshold. See tutorial understanding
the acoustic reflex.
dB SPL – decibels sound pressure level.
The type of decibel used in sound level meters, it compares the pressure of
sound at the microphone of the sound level meter to the reference pressure
of .0002 dynes/cm2.
Decibel: A decibel is a unit for expressing the
relative loudness of a sound. One-tenth of a bel, the decibel is a designation
of a unit of intensity on a logarithmic (non-linear) scale.
Decussation – crossing over of nerve fibers from one
hemisphere of the brain to the opposite (contralateral) hemisphere.
Auditory nerves will decussate at several places in the brainstem.
Degenerative Hearing Loss: A hearing
impairment that worsens over time.
Degree Of Hearing Loss: Terms utilized to
represent the thresholds of hearing graphed onto an audiogram to help describe
the different degrees of hearing impairment expected. One commonly used scale
is: mild = 25 to 40 dB, moderate = 41 to 55 dB, moderately-severe = 56 to 70 dB,
severe = 71 to 90 dB, and profound = greater than 90 dB.
Dendrite – portion of the neuron that connects either
to the sensory receptor (i.e. hair cell) or to the terminal button of the neuron
that is transmitting information (the neuron that comes “before” in the auditory
Digital: A more current type of hearing aid
that digitizes a sound, utilizing an analog-to-digital converter, prior to
processing the sound. Sound represented in a digitized format can be manipulated
and processed more efficiently.
Diplacusis: Perceiving a single tone as
multiple tones or multiple harmonics.
Direct Audio Input: A port on a hearing aid
that allows a hard-wired input of sound directly from an assistive listening
device into the hearing aid's electronic mechanisms (bypassing the external
Discrimination: In hearing terms, it refers to
the ability to distinguish between various tonal or speech sounds.
Dispenser: A hearing healthcare professional
who is trained to select, dispense, and adjust hearing aids.
Dri-Aid Kit: Various products containing
drying agents or utilizing heat that are used to lessen the amount of harmful
moisture built-up in a hearing aid.
DSP: Short for digital signal processing.
Refers to the range of volume between the level at which an individual first
hears a sound and the level at which that individual perceives the sound to be
Ear Canal: The external auditory meatus. The
hole in the temporal bone that tunnels the sound from the pinna to the ear drum
Eardrum: The tympanic membrane. A thin layer
of skin that separates the ear canal from the middle ear cavity. The eardrum
converts sound waves into vibrations.
Earhook: A portion of a Behind-The-Ear hearing
aid that is designed to bend over the top of the ear and connect the aid's
casing to the tubing.
Earmold – the portion of a behind-the-ear style
hearing aid that fits in the concha and directs the sound into the ear canal.
Eighth Cranial Nerve (CN VIII): The acoustic
or auditory nerve which runs from the inner ear to the brainstem which contains
fibers that carry auditory and vestibular information.
Earmold: A piece of molded material that fills
up some portion of the concha bowl and/or ear canal which is connected via
tubing to a behind-the-ear hearing aid for the purposes of holding the tubing in
place, sealing the canal, and modifying the sound.
Eng (Electronystagmography): A special series
of tests utilized to evaluate the vestibular system during which eye movements
are measured electro physically.
Endolymph – fluid in the section of the cochlea known
as scala media, and in the membranous labyrinth of the vestibular system.
This fluid is high in potassium and relatively low in sodium.
Entraiment: An undesired effect of some
anti-feedback circuitry in which the feedback reduction algorithm attempts to
eliminate an incoming sound as if the sound is feedback when it truly is not.
Equilibrium: A body's ability to maintain
physical balance by using vestibular, visual and proprioceptive (sense of touch)
Etiology: In hearing terms, the source or
cause of a hearing loss.
Eustachian Tube: A small connection between
the throat and the middle ear cavity which in the normal human ear system is
utilized to equalize the pressure in the middle ear cavity to the pressure in
the atmosphere surrounding the body.
Eustachian Tube Dysfunction: When the tube
that connects the throat and the middle ear cavity becomes inflamed or blocked.
Eustachian tube dysfunction can lead to negative pressure, fluid in the middle
ear, and/or middle ear infections.
Evoked Potentials: Electrical activity in the
body measured by electrodes that occurs as a result of a stimulus.
Exostosis: A bony growth in the ear canal.
External Auditory Meatus: Another name for the
ear canal or the acoustic meatus.
External ear – part of the auditory system comprised
of the pinna and external auditory meatus.
Feedback: The high-pitched whistling sound
that can be emitted by a hearing aid when the hearing aid's microphone picks up
its own output, thus re-amplifying itself.
Feedback Suppressor Or Cancellor: Technology
present in some newer hearing aids that is designed to limit the amount of
feedback experienced by hearing aid users. Low-end hearing aids lower gain to
reduce feedback, while more advanced hearing aids alter the phase of the signal
to control feedback.
Fistula: An abnormal hole or rupture in the
window that connects the middle ear cavity and the cochlea, allowing the leakage
of inner ear fluid (perilymph) into the middle ear and often resulting in
hearing loss and dizziness.
Flat Audiogram: A description of the graph of
an individual's hearing thresholds in which the degree of loss present is
similar or equal for low, mid and high frequencies.
Footplate – portion of the stapes bone that is
attached to the two crura and that sits in the oval window.
Frequency: Cycles per second. The number of
vibrations occurring during a second, resulting in the perceived "pitch" of a
Gain: A term used to describe the amount of
additional intensity added by a hearing aid or other amplifying device to an
incoming signal during the amplification process.
Genetic Hearing Loss: Congenital hearing loss.
Hearing loss that is present at or before birth.
Hair Cells: Cells present in the cochlea that
convert the mechanical energy present in sound vibrations into electrical
activity. Hair cells have cilia on one side which are stimulated by movement and
on the other side are connected to fibers of the VIIIth cranial nerve, which
carries the impulse to the brain.
Hard Of Hearing: A term used to describe
hearing-impaired individuals with mild to severe / profound hearing impairment
who are not deaf.
Head Shadow Effect: The knowledge that a
sound source presented on one side of the head is less intense when measured on
the other side of the head, due to the sound having to make its way around the
Hearing Aid: An electronic device which is
utilized by an individual with hearing loss to amplify sound and therefore make
the sound more audible.
Hearing aid dispenser – person licensed by the state
to dispense hearing aids, but who does not have university training in
Hearing Aid Specialist: A non-audiologist. A
hearing healthcare professional who holds a state license that allows him or her
to dispense hearing aids.
Hearing Disorder: A general term used to
describe any disruption in the normal auditory process.
Hearing Loss: The inability to perceive the
presence of a sound at normal hearing levels.
Helicotrema – the portion at the apex of the cochlea
where there is no scala media. The perilymph can flow between scala
tympani and scala vestibuli at this location.
Helix: The curved / raised rim of the external
Hereditary Hearing Loss: A hearing loss or a
propensity for hearing loss that is transferred via genes from parent to
Hertz (Hz): Cycles per second. A name given to
describe the frequency or pitch of a sound.
High Frequency Hearing Loss: A hearing
impairment which is only present or is significantly more prevalent in the
Immittance Measurements: Another name for
Impedance – an object or medium’s resistance to energy
flow. A high-impendance medium will reject energy; a low-impedance
substance vibrates more freely.
Impression: A mold of the concha and ear canal
made by a hearing healthcare professional to assist the hearing aid manufacturer
in producing a custom fit hearing aid that sits in and seals the user's ear
Incus: The middle bone of the ossicular chain.
Induction Coil: The telecoil inside of a
hearing aid that is activated by electro-magnetic energy coming from a telephone
or assistive listening device.
Infrared: A signal used by some assistive
listening devices to send sound via infrared light waves.
Inner Ear: The cochlea. The snail-like portion
of the ear system that converts mechanical sound energy coming from the middle
ear into an electrical impulse prior to transmission to the brain.
Inner hair cells – the cells within the organ of Corti
that are responsible for encoding neural impulses for sound. These
ciliated cells are located on the medial side of the arch of Corti, and are
found spiraling the length of the cochlea. Only one hair cell is seen on
any cross section of the cochlea, where 3 to 5 outer hair cells are found
sitting side by side.
Insertion Gain: The difference between the
amount of intensity present at the eardrum when a functioning hearing aid is in
an ear and turned on versus the amount of intensity present when there is no
hearing aid in the same ear.
In Situ: In place. The in situ gain of a
hearing aid is measured with the hearing aid in place in the ear.
Internal auditory meatus – the hole in bone through
which the nerves exit the cochlea on their way to the brainstem.
Intensity: The loudness or volume of a sound.
In-The-Canal (ITC) Hearing Aid: Smaller than
an ITE hearing aid, it usually fills up a portion of the ear canal and a small
portion of the outer ear. A mini-canal attempts to make the hearing aid even
smaller by using a smaller battery.
In-The-Ear (ITE) Hearing Aid: A style of
hearing aid in which all the parts of the hearing aid are fit into the concha or
bowl area of the pinna and the ear canal. Variations of ITE hearing aids are:
Full Shell: A type of ITE in which
the hearing aid fills up the entire bowl area.
Low Profile: A variation of a full
shell ITE, it too fills up the entire bowl area, but
is built thinner.
Half Shell: Smaller than a
full shell ITE, in that it is designed to fill up the bottom
1/2 or 1/3 of the bowl area.
Intraoperative Monitoring: Electrophysical
measurements of the auditory system made during a
surgery to monitor the effects
of the surgical procedure on the auditory system.
IROS (Ipsi-Lateral Routing Of Signal): A
designation for a hearing aid or earmold that has a large vent.
Kilohertz – (kHz). Thousands of hertz (cycles per
second of vibration). A measure of the frequency of sound.
Kneepoint: The sound level at which a
compression device inside a hearing aid starts to function. The point on the
slope of a hearing aid's input / output curve at which the linear amplification
common for soft inputs changes to the non-linear amplification for louder
Labyrinth: The hollowed-out area of the
skull's temporal bone that contains the cochlea and parts of the balance system.
Language Development Disorder (Hearing Related):
The lack of timely development of language skills by a hearing-impaired child
due to a detriment in the auditory input as a result of the child's hearing
Lateral lemniscus – nucleus of the auditory system
located after superior olive, but prior to inferior colliculus.
Lever action of the ossicles – the increase in force
of the movement of the incus (and thus the stapes footplate in oval window) that
is attributable to the fact that the malleus is longer than the incus, and thus,
like a lever, it moves the incus with greater force, though a shorter distance.
Levator veli palatini – muscle of the nasopharynx, one
of those responsible for opening the Eustachian tube.
Lateralization: The perception by an
individual that a sound is being heard on one side due to a timing and intensity
difference, when in fact the sound was presented bilaterally.
Linear / Non-Linear: A linear hearing aid is
one that adds the same amount of gain to the incoming signal, regardless of how
soft or loud the incoming signal is, up to a cutoff point or saturation. A
non-linear hearing aid is one that varies the amount of gain added to an
incoming sound based upon the intensity of the incoming sound. Usually in
non-linear hearing aids, soft incoming sounds have more gain added to them than
loud incoming sounds.
Lip Reading: See speech reading.
Listening Stethoscope: A device used by
hearing healthcare professionals to listen to a hearing aid for the purpose of
assessing the hearing aid's performance and adjustments / repairs.
Lobule: The ear lobe. The bottom part of the
pinna which does not contain cartilage.
Localization: The ability of the brain to
determine the direction from which the sound originated by utilizing differences
between the timing and intensity of a sound as perceived in one ear compared to
the other ear.
Loop System: A type of assistive listening
device that utilizes a small neck or large room loop to set up a magnetic field.
The system allows for a transfer of a desired signal, with less background noise
interference, to a hearing aid or other device using electro-magnetic energy.
Malingering: The faking of a hearing loss for
social or financial reasons.
Malleus: The first / hammer-shaped bone in the
ossicular chain, that is attached to the eardrum.
Manubrium of the malleus – portion of the malleus that
attaches to the tympanic membrane; the “handle” of the malleus.
Masking Noise: A sound introduced into an ear
system for the purpose of covering up an unwanted sound. Masking noises are used
during hearing tests to cover-up unwanted responses from a non-test ear.
Tinnitus maskers also utilize a masking noise to cover-up tinnitus.
Mastoid air cells – openings in bone, filled with air,
that are linked to the middle ear space. The opening between the middle
ear and pneumaticized (air-filled) mastoid cells is the aditus.
Mastoid Bone: A portion of the temporal bone
that is located behind the external ear. The bone conduction vibrator employed
during bone conduction testing is usually placed on the mastoid.
Mastoid process – the dome-shaped portion of the
mastoid bone that is behind the pinna. It is the location for the
placement of bone-conduction oscillators.
Medical Clearance: A statement from a
physician required before the dispensing of a hearing aid, unless a waiver is
signed by the patient, that states that there are no medical contraindications
to the use of a hearing aid.
Medial geniculate body – auditory nucleus located in
the brainstem, above the inferior colliculus. It is the last nucleus
before the auditory signal reaches the cortex.
Medium – The substance through which sound travels.
Sound is often defined as the vibration of the molecules of a medium. Air
is the most common medium.
Meniere's Disease: A name applied to a set of
symptoms (usually including vertigo, hearing loss, and tinnitus) that results
from an over-production of fluid in the endolymphatic sac of the inner ear
Microphone: The entry point for sound into a
hearing aid. The mechanism inside a hearing aid that converts sound waves into
an electrical signal.
Microtia: A congenital malformation of the
external ear. A condition in which an individual is born with an abnormally
small pinna and often a very small or absent ear canal.
Middle Ear: The portion of the human auditory
system located between the outer and inner ear, which uses the tympanic membrane
(eardrum) and ossicles (malleus, incus, and stapes) to transfer the sound via
vibration from the ear canal to the cochlea.
Middle Ear Effusion: When the body discharges
fluid into the middle ear cavity.
Mixed Hearing Loss: A hearing loss that has
both conductive and sensori-neural components.
Modiolus – the center core of the cochlea. The
first-order neurons (VIII nerve) runs through modiolus before exiting via the
internal auditory meatus.
Molecule – Smallest particle of a chemical element.
Hydrogen, nitrogen and oxygen are examples of molecules. Molecules are
comprised of protons, electrons and neutrons.
Monaural: Refers to when sound is presented
only to one ear (i.e., A monaural hearing aid fitting involves only one
Most Comfortable Level (MCL): A measurement
that is often made prior to the ordering of or programming of a hearing aid that
determines, for speech or tones, the intensity level that a patient considers to
be the most acceptable in regards to the overall comfort of the signal.
Mucous membranes – type of lining of the middle ear
and nasopharynx. It secretes mucus, a secretion of water, salts, skin
tissue cells, white blood cells, and a protein called mucin.
Multi-Band Hearing Aid: A programmable hearing
aid that allows the dispenser to adjust gain in a specified set of frequencies
without effecting gain at other frequencies.
Multi-Channel Hearing Aid: A programmable
hearing aid that allows the dispenser to adjust the instrument's compression
characteristics in a specified set of frequencies without effecting the
compression characteristics at other frequencies.
Multi-Memory Hearing Aid: A hearing aid that
has more than one dispenser adjusted listening program that the patient can
access to improve communication in various environments (i.e., memory one for
normal listening, memory two for noisy environments, and memory three for
Myelin – a fatty material that covers portions of some
neurons’ axons. Myelin insulates nerves from each other, and permits rapid
transmission of neural impulses as neural signals (action potentials) “skip”
across myelin sheathes, jumping from one node of Ranvier to the next.
Node of Ranvier – unmyelinated segments of axons,
between the myelin sheathes that cover the axon. The action potential is
conducted from one node to the next, allowing for a faster depolarization wave
than would occur in the neuron were not myelinated.
Noise-Induced Hearing Loss: A type of hearing
loss caused by the introduction of intense volumes into a human ear system over
long periods of time or very intense volumes for a short period of time. The
hearing loss often is worse on the side of exposure and is most pronounced in
the higher frequencies.
Nonorganic Hearing Loss: Symptoms of hearing
loss that are not associated with an obvious physical dysfunction of the
Nystagmus: Physical movement of the eyeballs
that occurs in a rhythmic nature when the vestibular system is over-stimulated
or spontaneously in certain abnormal vestibular systems.
Occlusion: The sensation that results from
"plugging up" the ear canal with cerumen, an un-vented hearing aid, or a foreign
Occupational Hearing Loss: The hearing loss
associated with the exposure to loud sounds in a work environment.
On-The-Ear (OTE) Or Open Ear Hearing Aid: A
more recently developed style of a BTE hearing aid that utilizes a thinner
tubing and a placement of the electronics lower down behind the ear for better
cosmetic appeal with less occlusion.
Organ Of Corti: The structure built upon the
basilar membrane inside of the spiral cochlea that contains the special sensory
receptors (hair cells).
Ossicular Chain: The three very small bones
located in the middle ear that are connected together to form a link between the
tympanic membrane (eardrum) and the cochlea. The three ossicles, called the
malleus, incus and stapes (hammer, anvil, and stirrup), transfer the sound
through the middle ear via vibrations.
Oscillation: Feedback. The whistling that
hearing aids can emit when an amplifier becomes unstable.
Oscillator: A device that is used to produce
vibrations, such as the bone conduction oscillator used during bone conduction
Otalgia: Ear pain or earache.
Otitis Media: Inflammation and/or infection of
the middle ear.
Otoacoustic Emissions (OAES): A test sometimes
performed during an audiological evaluation or screening that measures the
electrical activity emitted by a normal cochlea.
Otoblock: A sponge or piece of cotton that
usually has a string attached to it, used by a hearing healthcare professional
during the impression taking procedure necessary to the ordering of a custom fit
hearing aid, to prevent the impression material from going too deep into the ear
Otolaryngologist: An Ear, Nose, and Throat
Otologist: An ENT physician who
specializes in the evaluation and treatment of the ear.
Otorrhea: Drainage from the ear often caused
by an external ear infection or a middle ear problem with a tympanic membrane
Otoscope: A magnifying and lighting tool
utilized by health care workers to look into the ear canal.
Otoscopic Examination: The use by a healthcare
professional of the lighted and magnified vision provided by an otoscope to
evaluate the integrity of the pinna, ear canal and eardrum
Otosclerosis: An abnormal condition of the
middle ear in which there is a formation of spongy bone onto the footplate of
the stapes, resulting in a conductive hearing loss.
Ototoxic Medications: Prescription or
over-the-counter drugs that can have a temporary or permanent detrimental effect
on an individual's hearing or balance system.
Outer Ear: The most peripheral aspect of the
human auditory system that includes the auricle (pinna) and external auditory
meatus (ear canal).
Outer hair cells – the cells within the organ of Corti
that are responsible for increasing the amount of basilar membrane movement when
soft sounds are present. These ciliated cells are located on the radial
side of the arch of Corti, and are found spiraling the length of the cochlea.
Three to five outer hair cells sit side-by-side when viewing a cross section of
the cochla. The cilia of the outer hair cells are embedded in tectorial
Output Limiting: The various parameters
designed into a hearing aid by a manufacturer that controls the upper limits of
total volume (input + gain) that a hearing aid can produce.
Oval Window: A connection between the stapes
footplate of the middle ear and the fluid filled inner ear through which sound
vibrations pass in a normal auditory system.
Pars tensa - portion of the tympani membrane
that contains the fibrous middle layer and comprises most of the area of the
tympanic membrane. See also pars flaccida.
Pars flaccida – the portion of the tympanic membrane
that does not contain a fibrous middle layer, but only has the skin and mucous
membrane layers. It is located at the top of the tympanic membrane.
Patulous Eustachian Tube: An annoying
condition in which the eustachian tube, which normally opens and closes, remains
open. This condition can result in an increase in an individual's perception of
the sound of their own voice.
Pediatric Audiologist: An audiologist who
specializes in the evaluation and (re)habilitation of children.
Perforated Tympanic Membrane: A hole in the
Perilymph – the inner ear fluid found in scala
vestibuli and scala tympani. This fluid is high in sodium and relatively
low in potassium.
Period – the time required for one complete cycle of
vibration to occur.
Peripheral Hearing Loss: Hearing loss due to a
dysfunction of the auditory structures located outside of the central nervous
P.E. Tubes: Pressure equalization tubes placed
into the tympanic membrane (eardrum) for the purpose of keeping pressure levels
in middle ear cavity equal to atmospheric pressure.
Physiology – the study of the function of the
body, that is, how things work.
Physics – the study of the physical properties
of matter and energy. Acoustics is a branch of physics that studies
how sound vibration occurs.
Pinna: The auricle. The cartilaginous
structures of the external ear located peripheral to the skull.
Potentiometer: An external screw-adjusted
control on the outside of a non-programmable hearing aid utilized to change the
performance of the hearing aid's amplification parameters.
Power Hearing Aid: A hearing aid designed
specifically for individuals with severe to profound hearing losses to provide
the appropriate amount of extra gain needed to match their specific losses.
Prelingual Hearing Loss: Hearing loss that
occurs prior to a child developing speech and language skills.
Presbycusis: Hearing loss that is attributed
to the aging process.
Probe Microphone Measurements: The use of a
soft tube placed in the ear canal near the eardrum to evaluate the performance
of a hearing aid while it is in the ear or the ear's natural resonance. The soft
tube is attached to a microphone that is connected to a real ear analyzer.
Programmable: A helpful feature on more
current hearing aids that allows them to be attached, via a cord, to a computer
in a hearing healthcare professional's office. Once attached, the various
parameters of the hearing aid's performance can be more easily adjusted to
better match an individual's communicative needs. More expensive hearing aids
tend to have more parameters available for adjustment than less expensive
hearing aids, often making them more adaptable.
Pts (Permanent Threshold Shift): The presence
of some amount of hearing loss that is permanent.
Pumping: A fluctuation in volume noticed by a
hearing aid wearer due to the instrument's compression characteristics.
Pure Tone Audiometry: Refers to the part of a
complete hearing evaluation that includes the measuring of air-conduction and
bone-conduction thresholds while using non-complex (pure) tones.
Pure Tone Average (PTA): The average of the
air-conduction thresholds of the three middle frequencies, usually 500 Hz, 1000
Hz, and 2000 Hz. For flat or gently-sloping shaped hearing losses the Pure Tone
Average often correlates with the Speech Reception Threshold. Sometimes the
average includes other combinations of frequencies (i.e., a high frequency
average may include 3000 Hz or 4000 Hz).
Quality Of Life: In hearing terms, it refers
to the increased ability to enjoy and pursue daily activities when a hearing
loss is addressed with amplification.
Rarefaction – The portion of a sound wave where the
air molecules are most spread apart and have the lowest pressure. See also
the tutorial on acoustic review.
Real Ear: A measurement made with a dedicated
piece of equipment (real ear analyzer) that shows the performance of a hearing
aid while present in the user's ear. A real ear assessment usually requires that
a small probe be placed into the ear canal so that measurements of both pre- and
post-placement of the hearing aid can be analyzed. Real ear testing generally
utilizes an input of a series of tones that are then measured inside the ear
canal after passing through the hearing aid.
Real Ear Aided Response: The sound measurement
achieved by a probe tube placed into an ear canal when a hearing aid is inserted
into the ear and turned on.
Real Ear Unaided Response: The sound
measurement achieved by a probe tube placed into an ear canal without a hearing
aid in it. This is the measurement of an ear canal's natural resonance.
Real Ear Occluded Response: The sound
measurement achieved by a probe tube placed into an ear canal when a hearing aid
is inserted into the ear and turned off. This is the measurement of a hearing
aid's occlusion effect on the ear.
Receiver: The speaker inside a hearing aid
that converts the amplified electrical energy to sound waves.
Recruitment: A condition often occurring with
a sensori-neural hearing loss that results in an abnormal growth in loudness.
For someone with hearing loss who experiences recruitment, a specific increase
in intensity is perceived as a significantly larger increase in loudness than a
normal hearing individual would perceive the same increase in intensity.
Reissner’s membrane – the membrane separating scala
media and scala vestibuli in the cochlea.
Relay Service: An operator who helps TTY users
communicate via telephone to non-TTY users by listening to the auditory signal
and typing out the words or reading the TTY user's words and relaying them to
the non-TTY user.
Resonance – enhancement of sound at a certain
frequency because of the characteristics of the vibrating object or tube.
Cavities of different lengths resonate, or accentuate sound vibration, at
certain frequencies. Objects will vibrate best at a given frequency or
frequency range, depending upon the mass and stiffness of the object.
Retrocochlear: A designation for the part of
the human auditory system that includes the acoustic nerve, the brainstem and
Reverberation: The interference noted when an
individual hears sounds "bounce" around the inside of a room.
Reverse-Slope Audiogram: A description of the
graph of an individual's thresholds in which the hearing is poorer in the lower
frequencies and the hearing loss is less pronounced or the hearing is normal in
the higher frequencies.
Round window – membrane-covered opening between the
scala tympani of the inner ear and the middle ear.
Saccule – located in the vestibule of the inner ear,
this structure along with the utricle sense “straight line” head motion.
Scala media – the middle section of the cochlea,
which contains endolymph. Basilar membrane is at the bottom of scala
media; Reissner’s membrane is at its top.
Scala tympani – the section of the cochlea that
is below basilar membrane and contains perilymph. If a cross section
of one coil of the cochlea is examined, scala tympani will be on the bottom.
Scala vestibuli – the section of the cochlea
that is above Reissner’s membrane and contains perilymph. If a cross
section of one coil of the cochlea is examined, scala vestibuli will be on
Screening (Hearing): An evaluation of the
auditory system that is generally not as in-depth as a traditional hearing test
and often does not include the actual assessment of an individual's thresholds,
but instead results in "pass" or "fail".
Semicircular Canals: The three fluid-filled
tubes in the vestibular portion of the inner ear that helps with equilibrium and
the interpretation of the body's position.
Sensori-Neural Hearing Loss: A decrease in an
individual's ability to hear a particular sound due to a problem in the inner
ear (cochlea) or the neural system (Cranial Nerve VIII). The designation of a
hearing loss as sensori-neural suggests that the sound makes it way through the
outer and middle ear systems efficiently, but is not picked-up by the hair cells
in the cochlea or transmitted by the hearing nerves as well as an average normal
human ear's system.
Shrapnell’s membrane – a synonym for pars flaccida.
Signal-To-Noise Ratio: The relationship
between the intensity of the desired sound (signal) and other undesired sounds
(noise). The louder the speech signal is presented in comparison to the
background noises, the better chance a person has at understanding the speech
Sign Language: The use of hand and body
movements to communicate language information.
Simple harmonic motion – the vibration back and forth
of an object or air molecules that results in a clean single tone, a “pure
tone”. See also tutorial on acoustics review.
SNHL: Sensori-neural hearing loss.
Soma – the body of a nerve cell.
Sound Booth: A sound treated enclosure that is
designed to attenuate the interference of extraneous sounds during a hearing
test. Sound booths lessen but do not eliminate reverberant and ambient noises.
Sound Field Hearing Aid Testing: The analysis
of the performance of a hearing aid in which a patient's thresholds are
measured, while in a sound booth with the stimuli presented through a speaker
system, with and without a hearing aid inserted.
Speech Audiometry: The portion of an
audiological evaluation that uses speech stimuli to measure the auditory system.
Speech audiometry testing often includes the measurement of Speech Reception
Thresholds (SRTs) utilizing two-syllable spondee words and the assessment of
Word Recognition / Speech Discrimination scores utilizing single syllable words
in a carrier phrase. Some speech audiometry tests use sentence materials instead
of single word materials.
Speech-language pathologist – health care professional
who assess speech and language development and treats language and speech
Speech Mapping: A variation of the traditional
real ear analysis, during which a professional uses a special device to measure
the performance of a hearing aid using speech as the input instead of a series
Speech Reading: The use of lip reading and
other visual cues produced by a speaker to help with the understanding of spoken
Speech Reception Threshold: The use of
familiar two-syllable spondee words by a hearing healthcare professional to
assess the lowest intensity level at which an individual can repeat the words
more than half of the time.
Spiral limbus – a part of the organ of Corti that is
one point of attachment for tectorial membrane. It is composed of
periosteum, the type of tissue that covers bone, and is located on top of the
bony ridge called osseous spiral lamina.
Stapedius – a muscle residing in the pyramidal
eminence on the posterior wall of the middle ear space whose tendon is attached
to the neck of the stapes. Contraction of the stapedial muscle (e.g. in
response to loud sound) increases the stiffness of the middle ear system and
reduces the transmission of low-frequency sound through the middle ear.
Stapes: The smallest and last bone in the
ossicular chain. It attaches to the oval window of the inner ear.
Stria vascularis – a lining of the radial wall
of scala media, containing a rich network of vascularized tissue (containing
networks of small veins and arteries). Endolymph is produced and
nourished by stria vascularis.
Superior olivary complex – a nucleus in the
auditory central nervous system, located just after cochlear nucleus and
prior to lateral lemniscus.
Swimplugs: Material used to keep water out of
the ear canal. They can be custom or non-custom made and are often used to
prevent infections that can result from water getting into the ear canal or
middle ear cavity.
TDD: Telecommunication device for the deaf. A
special device that allows for the transmission of and reception of words over
phone lines via a typewritten signal.
Tectorial membrane – a gelatinous tissue mass that is
located above the hair cells. The cilia of the outer hair cells imbeds in
Telecoil: A coil placed inside of a hearing
aid that picks up electro-magnetic energy emitted by certain telephones and
assistive listening devices.
Temporomandibular joint – (TMJ), the hinge joint for
Tensor tympani - a muscle residing in the
semicanal of tensor tympani on the medial wall of the middle ear space whose
tendon is attached to the malleus. Contraction of the tensor tympani
muscle would move tympanic membrane inward and decrease the vibration of the
TM by increasing the stiffness of the middle ear system.
However, in humans this muscle does not appear to contract in response to
Tensor veli palatini – muscle of the
nasopharynx, one of those responsible for opening the Eustachian tube.
Threshold Of Hearing: The lowest level that a
particular sound's presence can be perceived by an individual more than half of
Tinnitus: The perception of the presence of a
sound in one or both ears that is not associated with an external sound source.
Tinnitus can be described as constant or intermittent and of various volume
levels, pitches, and complexities (ringing, roaring, hissing, crickets,
whistling, rushing, etc.).
Tonotopic organization – the property of a structure
to be organized such that different locations within the structure respond to or
encode different frequencies. (There is a different place within the
structure for each frequency.)
Tragus – the skin covered appendage in front of the
pinna. The tragus can be pushed inward to cover the entrance of the ear
Transmitter: The portion of a CROS system that
picks up a signal on one side of the head and sends it via a hard wire or an FM
signal to the receiver on the other side of the head.
Trapezoid body – nerve fiber pathway in the lower
brainstem that decussates from one hemisphere to the other. The trapezoid
body contains a nucleus, called the nucleus of the trapezoid body.
Traveling wave – an undulating up and down motion of
basilar membrane in response to sound that increases in amplitude relatively
gradually until it reaches a maximum displacement point, and then decreases in
amplitude rapidly just apical to that point of maximum vibration.
Tunnel of Corti – space beneath the arch of
Tuning fork – hand-held device that produces
tones that are essentially pure tones. Tuning forks of different sizes
produce different frequency tones.
TTS (Temporary Threshold Shift): The presence
of some degree of hearing loss, often induced by noise or chemical exposure,
that recovers over time.
Tympanic Membrane: Another name for an
eardrum. It is the membrane that separates the ear canal and the middle ear
cavity. The tympanic membrane vibrates when hit with sound waves, causing the
ossicular chain to vibrate.
Tympanogram: A chart onto which the compliance
results of tympanometry are graphed.
Tympanometry: A test, also referred to as
immittance testing, done during an audiological evaluation that helps to assess
the integrity of the tympanic membrane (eardrum) and the middle ear cavity.
During tympanometry testing, a probe is inserted into and sealed in the ear
canal and then a reflected tone is measured as the pressure in the ear canal is
changed. The results are often graphed onto a tympanogram, showing the
compliance at various positive and negative pressure levels.
Uncomfortable Loudness Level (UCL): A
measurement that is often made prior to the ordering of or programming of a
hearing aid that determines, for speech or tones, the intensity level at which a
patient judges a particular signal to be uncomfortably loud.
Umbo – the center-most point of the tympanic membrane
and the point at which the tympanic membrane is most medially displaced.
The manubrium of the malleus is attached at the umbo, and its medial pull
creates the cone shape of the eardrum.
Unilateral: Pertaining to only one ear or one
side of the head (i.e., The person with a hearing loss on the right but not the
left has a unilateral hearing loss.).
Utricle – located in the vestibule of the inner ear,
this structure along with the saccule sense “straight line” head motion.
Vent: A hole placed in a hearing aid or
earmold to modify the amount of occlusion effect noted by a hearing aid wearer
or to adjust the frequency response of the hearing aid.
Vertigo: A sensation of spinning experienced
by individuals with vestibular problems.
Vestibular System: The inner ear portion of
the balance system.
Vestibule – portion of the inner ear that is between
the cochlea and the semicircular canals. Oval window is located in the
Vestibulocochlear Nerve: Another name for the
auditory nerve or the VIIIth cranial nerve which connects the cochlea to the
brainstem and is made up of both auditory and vestibular nerve fibers.
VIII nerve – also called the acoustic nerve or more
correctly, the vestibulo-acoustic nerve. It conveys information from the
cochlea, utricle, saccule and semicircular canals to the brainstem.
Visual Reinforcement Audiometry: A procedure
used when testing the hearing of very young patients. The young patient is
trained to associate a sound with an interesting visual experience (such as a
flashing light or an animated stuffed animal) so that future presentations of
audible sounds elicit head movements
Volume Control: A wheel or button on the
faceplate of a hearing aid or on a remote control utilized by a hearing aid
wearer to increase or decrease the instrument's gain.
Wavelength – when a pure tone is produced, the sound
radiates outward. As it does, different areas (of air) are in rarefaction
and compression. Wavelength is the physical distance, generally measured
in feet, between areas where the sound wave is in the same phase of vibration.
For example, if air molecules are in maximal compression at one place, and then
are rarefied one foot later, then maximally compressed again two feet away from
that original compression place, then the wavelength is 2 feet. Wavelength
is related to frequency and computed by dividing the speed of sound by the
Wax Loop: A small tool used by professionals
and hearing aid users to clean ear wax out of the tubing of a hearing aid.
WNL: Within normal limits.
Word Recognition Score: The percentage of a
list of speech stimuli that an individual is able to repeat.