Aided Thresholds - Represented by the symbol "A" on an audiogram, they are the softest tones that a person can hear while wearing hearing aids.

Air Conduction - Air conduction thresholds are obtained by using the earphones of an audiometer, with the symbol "O" representing right ear sensitivity and the symbol "X" representing left ear sensitivity on an audiogram. 

Audiogram - A graph of a person's peripheral hearing sensitivity with frequency (pitch) on one axis and intensity (loudness) on the other.

Bone Conduction - Measurements of hearing through a vibrator placed on the mastoid bone behind the ear.  Therefore, the cochlea of the inner ear and the VIII nerve are tested.  The outer and middle ears are not tested.

Cochlea - A spiral-shaped, fluid-filled inner ear structure; it is lined with cilia (tiny hairs) that move when vibrated and cause a nerve impulse to form.

Conductive Hearing Loss - A hearing loss caused by damage or disease (pathology) located in the outer or middle ear that interferes with the efficient transmission of sound  into the inner ear where sound reception occurs.

Decibel (db) - The logarithmic unit of sound intensity or sound pressure; 1/10th of a Bel.

Eardrum - (also called the tympanic membrane) A thin membrane that vibrates when sound waves reach it.

Eustachian tube - A tube that connects the middle ear to the back of the nose; it equalizes the pressure between the middle ear and the air outside. When you "pop" your ears as you change altitude (going up a mountain or in an airplane), you are equalizing the air pressure in your middle ear. 

Frequency (Pitch) - The number of times that any regularly repeated event, such as sound vibration, occurs in a specified period of time, usually measured in cycles per second.  Also called pitch and measured in Hert (Hz) along the top of an audiogram from low to high-frequency sounds; low-frequency sounds are mose commonly associated with vowel sounds and high-frequency sounds with consonants.

Hertz (Hz) - A unit of frequency measurement equal to 1 cycle per second.

Incus - A tiny bone that passes vibrations from the hammer to the stirrup.

Inner ear - comprised of the cochlea, which contains hair cells, the thousands of tiny receptors of sound, the vestibular or balance system, and the acoustic nerve that transmits nerve impulses from the inner ear to the brain. 

Intensity (Loudness) - Intensity also is referred to as loudness and is measured in dB.

Malleus - A tiny bone that passes vibrations from the eardrum to the anvil.

Middle ear - The part of the auditory mechanism that functions to conduct sound effeciently into the inner ear; made up of the eardrum (tympanic membrane), a small air-filled space, and the three smallest bones in the body (ossicles: malleus, incus, stapes).

Nerves - These carry electro-chemical signals from the inner ear (the cochlea) to the brain.

Otitis media - Also known as middle ear infection, it is the most common cause of conductive hearing loss in children.  It is an inflammation of the middle ear, typically with fluid present in the normally air-filled middle ear cavity.

Outer ear -The part of the hearing mechanism made up of the pinna and external auditory meatus (ear canal), that functions to protect and channel sounds into the middle ear.

Outer ear canal - The tube through which sound travels to the eardrum.

Pinna - (also called the auricle) The visible part of the outer ear. It collects sound and directs it into the outer ear canal.

Semicircular canals - Three loops of fluid-filled tubes that are attached to the cochlea in the inner ear. They help us maintain our sense of balance.

Sensorineural Hearing Loss - Often called a "nerve loss/impairment", a sensorineural hearing loss results from disease or damage located in the inner ear; usually a permanent hearing loss.

Sound level - The intensity of sound in decibels.

Stapes - A tiny, U-shaped bone that passes vibrations from the stirrup to the cochlea. This is the smallest bone in the human body (it is 0.25 to 0.33 cm long).

Threshold - The intensity at which an individual can just barely hear a sound 50% of the time; all sounds louder than threshold can be heard, but softer sounds cannot be detected.