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The Hearing Dictionary Online - A, B, C

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ABR - see Auditory Brainstem Response

Acoustic Feedback - howl or whistle caused by the recirculation of acoustic output of an amplifying system. In a hearing aid the sound emanating from the receiver may reach (or feed back into) the microphone and be reamplified until it builds up into a high-pitched whistle.

Acoustic nerve - the eighth cranial nerve, combining the nerves of hearing (cochlear) and balance (vestibular). Also called: auditory nerve, vestibulocochlear nerve

Acquired Hearing Loss - hearing loss which develops after birth as a result of injury or disease

Aid, hearing - electric amplifying device to make sounds audible to the individual with a hearing loss. Sound pressure waves are converted into electricity by a microphone. The electric impulses are then amplified through controlled electronic circuitry. The amplified electric impulses are then reconverted by a receiver (earphone) to pressure waves at a much more intense level to be presented to the impaired ear

Air Blower - an instrument used to dry earmolds

Air Conduction - the transmission of sound through the outer and middle ear to the inner ear

ALD (Assistive Listening Device) - A device to help a person hear better, that is not a hearing aid. eg. amplifying telephones, vibrating watches etc.

Amplifier - the device in the hearing aid that makes sound louder.

Analog Hearing Aid - Hearing aids that use an analog circuit to analyze and process sound.

Anotia - congenital absence of the pinna

Anoxia - lack of oxygen. Sensorineural hearing loss can also be caused by prematurity and anoxia. Anytime there is a lack of oxygen to the brain, hearing can be affected.

Antihelix - A landmark of the outer ear.

Assistive Listening Devices (ALD) - products which amplify sounds in situations that people require assistance to hear a specific sound from a specific source.  Can be used with or without a hearing aid.  Some examples are telephones that flash when ringing and close captioning on television.

Atresia/Atretic - absence of a body opening such as an ear canal

Audiogram - a graphic representation of hearing threshold at different pitches and different loudness levels

Audiologist - A person with at least 6 years of University training, that tests, counsels and helps people that have concerns about their hearing. A licensed hearing care professional who specializes in the identification, assessment and treatment of hearing loss and the fitting of hearing aids. Audiologists hold graduate degrees in the field of hearing, and are experts in the measurement of hearing loss.

Audiology - study of hearing and hearing impairment. In Europe the term usually includes the study of the nature, causes, and treatment of diseases of the ear.

Audiometric Zero - see Zero Hearing Level

Auditory Brainstem Response (ABR) - a test that measures the amount of time that it takes for sound to reach the auditory areas of the brain

Auditory Ossicles - The three small bones in the middle ear, know as the hammer (malleus), anvil (incus) and stirrup (stapes) which are connected to one another. Together these ossicles are called the ossicular chain. Their purpose is to lead the sound striking the eardrum further into the inner ear.

Auditory System - all of the components from the pinna(outer ear) to the brain that are responsible for hearing

Auricle - the most visible portion of the outer ear. Cartilaginous structure located on the side of the head; also called the pinna. The auricle collects sounds from the environment and funnels them into the ear canal.


Bacterial Meningitis - inflammation of the membranes covering the brain and spinal cord. This viral infection may cause hearing loss. It does not always lead to hearing loss, but it can cause a wide range of sensori-neural hearing loss from monaural to binaural and mild to profound in degree.

Battery - a cell that stores an electrical charge and furnishes a current

Behavioral Observation Audiometry (BOA) - a hearing test in which the audiologist observes the child for changes in behavior in response to an auditory stimuli

Behind-the-Ear Hearing Aid (BTE) - a hearing aid which fits behind the outer ear and is coupled to the ear canal via an earmold and tubing

Bilateral - pertaining to two sides or two ears

Binaural - pertaining to both ears

BOA - see Behavioral Observation Audiometry

Body Aid - a hearing aid which has all of the components encased in a small box which is usually worn on the chest; a cord connected to the body aid connects to an earmold worn in the ear 

Bone Conduction - the pathway sound travels to the inner ear that bypasses the outer and middle ear systems

Bone Conduction Hearing Aid - in this hearing aid, an amplified signal is sent to a bone vibrator; which is placed behind the outer ear on the mastoid; this signal bypasses the outer and middle ear and stimulates the inner ear (cochlea) directly 

BTE - see Behind-the-ear Hearing Aid



Canal, Spinal Cochlear - commonly known as the spiral canal of the cochlea. A portion of the bony labyrinth of the inner ear about 30 mm long making 2 3/4 turns about a central bony supporting structure known as the modiolus. Contains the scala tympani, scala vestibuli and cochlear duct. Also referred to as Rosenthal's canal.

CAPD - see Central Auditory Processing Disorder

Cartilage - connective tissue between bone and epithelium (skin)

Central Auditory Processing Disorder (CAPD) - disorder in the function of the central auditory structures; characterized by difficulty understanding speech in noise and localizing sounds

Cerumen - yellow or brown wax-like substance (earwax) secreted in the outer one-third of the external ear canal by the ceruminous glands. adj:ceruminal, ceruminous.

Chicken Pox - a highly contagious, infectious virus characterized by a blister-like rash and mild fever due to vericella-zostervirus, a member of the herpes family. Although rare, some complications which may occur are chest infections (like bronchitis and pneumonia), sinusitis and otitis media (middle ear infection). 

Cholesteatoma - a cyst-like mass lined with skin cells containing shed skin and cholesterol; usually begins in the middle ear resulting from a perforation of the eardrum or from chronic otitis media. The skin grows and may become infected with bacteria at which point it may cause drainage and a foul-smelling odor. Surgery is often recommended since this infection could corrode the middle ear bones or move into the mastoid cavity.

Closed Captioning - "subtitiles" or translations of the spoken word to the written allowing deaf and hard-of-hearing people to see what they cannot hear. There are two kinds of captioning--open and closed. Open captions always appear on the screen, while closed captions must be enabled to be seen

CMV - see Cytomegalovirus

CIC hearing aid - see Completely-in-the-Canal Hearing Aid

Crest of Helix - A landmark of the outer ear.

Cochlea - winding tubular cavity within the inner ear, shaped like a snail-shell; contains the end-organ of hearing which finally changes the pressure waves of sound into nerve impulses. The central bony support of the cochlea is called the modiolus. A thin bony plate, the spiral lamina, extends from the modiolus and partially divides the cochlea. The division is completed by the fibrous support for the organ of Corti - the basilar membrane. One passageway above the divider begins at the oval window - the scala vestibuli. Another begins at the round window - the scala tympani. They are joined at the apex or helicotrema. Between the two is the scala media, or the cochlear duct, which contains the organ of Corti. When extended the cochlear is about 1 1/3" (35 mm) long.It has 2 3/4 turns and is about 5 mm high and 9 mm in diameter. adj: cochlear.

Cochlear Implant - a sensory aid  which is implanted surgically into the cochlea when severity of hearing loss and situation warrant. It is an electronic device that provides a sensation of hearing for profoundly deaf persons who are unable to obtain significant benefit from conventional high-powered hearing aids.A cochlear implant consists of two basic parts: an externally worn device and an internal, surgically implanted device

Completely-in-the-Canal Hearing Aid (CIC) - a small custom hearing aid which fits almost entirely within the ear canal; this placement allows more gain with less power since the hearing aid is closer to the eardrum. Currently the CIC hearing aid is the smallest hearing aid made.

Composite Noise - a sound stimulus generally composed of a large number of individual sinusoidal signals summed together for simultaneous presentation. The result is a "noise-like" stimulus with controlled spectral characteristics. Commonly used to mimic the spectrum of spoken speech.

Compression Amplification - method of limiting (or compressing) the amplification of loud sounds in comparison to weak sounds. When this type of circuit is used in a hearing aid or other amplifier, the wave form of a loud sound is less modified than when peak-clipping is used.

Concha - shell or bowl-like depression of the outer ear which funnels sound to the ear canal

Conditioned Orientation Reflex (COR) - a technique for testing children in the soundfield, through loudspeakers, where the child looks towards the sounds presented in search of a lighted toy

Conductive Hearing Loss - one of three types of hearing loss (sensorineural and mixed hearing loss being the other two types.) Produced by injury to, or problems with, the bones, eardrum and membranes which carry sound from the external ear through the  to the inner ear.

Cone of Light - light reflection visible on the eardrum during otoscopy

Congenital - present at birth

Congenital hearing loss - hearing loss present at birth

Congenital Malformation - a part of the anatomy irregularly shaped at birth

Craniofacial - pertaining to both the face and the cranium (skull)

Cytomegalovirus (CMV) - a member of the herpes family common to humans; can cause hearing loss when contracted by the mother during pregnancy in the first or second trimester. It is a prenatal or postnatal infection, usually transmitted in utero, which can have adverse effects on the central nervous system including loss of hearing and vision. It can have a delayed onset and it can also be progressive. CMV needs to be monitored both medically and audiologically. 

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HearingCentreOnline.com would like to thank and acknowledge Starkey Labs and Siemens Hearing for their generous contributions of some of the definitions in this online dictionary of hearing terms.

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