Audiology

C

Canal Hearing Aid

A hearing aid that fits entirely within the ear canal.

Central auditory processing disorder (CAPD)

A language disorder that involves the perception and processing of information that has been heard. Children with CAPD have problems following spoken instructions and usually show other language-learning problems, even though the inner ear is functioning normally.

Cerumen

aka Ear wax; Wax secreted from glands in the ear canal that keeps the skin of the ear dry and protects it from infection.

Cholesteatoma

A non-cancerous tumor where skin cells grow uncontrolled (usually through a hole in the eardrum) and accumulates in the middle ear. It may also be the result of chronic otitis media. A cholesteatoma damages the middle ear and surrounding structures and needs to be surgically removed.

Closed captioning

Displaying text of spoken words, often placed at the bottom of movies or television screens. This allows a hard of hearing viewer to follow the dialogue (even though he can't hear it) and the action of a program simultaneously. Closed captioning may be turned on or off at will by the person watching the TV.

Cochlea

'The auditory portion of the inner ear consisting of fluid-filled channels containing the hair cells. The cochlea is shaped like a small snail shell and normally consists of two and a half turns. The cochlea converts incoming sound waves from the middle ear into electrical signals and transmits these signals to the auditory nerve.

Cochlear implant

A device that substitutes for damaged (dead) hair cells of the inner ear. It consists of an electrode array that is surgically implanted in the cochlea. It delivers electrical signals to the auditory nerve from an external processor, enabling people with severe to profoundly hearing loss to perceive sound again. Cochlear implants are an option if hearing aids do not give you significant benefit.

Conditioned audiometry

A type of hearing testing used with young children. Children are trained (conditioned) to perform some activity (e.g. dropping a block in a box, pressing a toy button, put a peg in a hole etc.) in response to sounds. The audiologist uses an audiometer set at varying levels of loudness to assess the child's hearing loss.

Conductive hearing loss

A form of hearing loss arising in the external ear canal, ear drum or middle ear. It refers to anything that impedes or blocks the passage of sound through the outer and/or middle ear sections by preventing or not effectively transmitting sound to the inner ear. A conductive loss could result from something blocking the ear canal, from a ruptured ear drum, or from anything that restricts the movement of the bones in the middle ear. The most common cause of conductive hearing loss is fluid (infection) in the middle ear (otitis media).

Congenital hearing loss

A hearing loss present at birth, or associated with the birth process, or which develops in the first few days of life. It may or may not be hereditary.

Contralateral routing of sound hearing aid (CROS)

A hearing aid designed for a person who has normal hearing in one ear and is deaf in the other. This hearing aid picks up sounds on the non-hearing side and transmits them to the good ear so the person wearing a CROS aid can hear people speaking from his deaf side.

Cued speech

A visual representation of the phonemes of spoken language that uses 8 hand-shapes in 4 different locations (cues) on the face in combination with the natural mouth-movements of speech to distinguish all the sounds of spoken language.

D

Decibel (dB)

Scale based unit measuring loudness.

Digital hearing aid

A hearing aid that provides amplification by processing sounds as bits (numbers) instead of as a voltage. This is the way computers work. Digital hearing aids can control or modify sound in almost an infinite number of ways through its programs

Direct audio input (DAI)

The capability of connecting a sound source, such as a TV or CD or DVD player directly into a hearing aid. DAI bypasses the hearing aid's microphone by plugging a cord connected to a sound source directly into the hearing aid. Most hearing aids do not have the necessary DAI connections (called boots or shoes) so you have to ask for this specifically if you want it. Sometimes used to refer to the connection of an FM auditory trainer directly into a hearing aid.

Discrimination

Hearing clarity—the ability to tell apart (discriminate between) similar-sounding words such as "fun" and "sun." People with normal hearing generally have 100% discrimination. If your discrimination scores drop below 40% to 50%, you won't understand much of what you hear, no matter how loud it is. Speech then sounds more like gibberish or a foreign language. Discrimination is always expressed as a percentage. Now called Word Recognition (WR) testing.

Dynamic range

The range of loudness between the softest sound that a person can hear and the loudest sound they can stand (Uncomfortable loudness level). Hearing aids should be adjusted to keep all sounds within this range—although this is not always possible if you have a severely-collapsed dynamic range. The normal dynamic range is about 120 dB, while the dynamic range of a person with a severe or profound hearing loss may only be about 30 dB.

E

Eardrum perforation

 A hole in the eardrum.

Ear impression

An impression of the ear canal made to determine the exact size and shape of an ear. The impression is used to make in-the-ear hearing aids, earmolds for BTE hearing aids or custom-made ear plugs.

Early intervention services

Services provided by both public and private agencies to infants and toddlers and their families. These services are designed by law to support families in enhancing a child's potential growth and development from birth to age three.

Earmold

The part of a behind-the-ear hearing aid that fits into the ear and directs sound from a BTE hearing aid into the ear canal. It also helps hold the hearing aid in place. It can be made of materials such as plastic or vinyl.

Electronystagmography (ENG)

A battery of tests that evaluate the interaction between the balance parts of your inner ear and your eye muscles.

Eustachian tube

The small tube connecting the back of the throat to the middle ear that allows air into the middle ear and allows naturally-occurring fluid to drain from the middle ear. During yawning and swallowing it temporarily opens to supply air to the middle ear and to equalize the pressure in the middle ear to that of the outside atmospheric air pressure.

EVAS (Enlarged Vestibular Aqueduct Syndrome)

A genetic condition where the vestibular aqueduct is larger than normal. The result is that many people with enlarged vestibular aqueducts suffer from hearing loss from head trauma or from rapid changes in pressure.

F

Feedback

A high-pitched whistle or squeal that's made when an amplified sound is picked up by a microphone and re-amplified. For example, it occurs when the sound coming out of a hearing aid leaks out of the ear canal, gets back into the hearing aid's microphone and is amplified over and over until all it does is howl at its maximum loudness. Feedback can be caused by as earmold or hearing aid that does not fit properly, from a cracked or damaged earmold (or tube in BTE hearing aids) or from a damaged hearing aid. Many modern digital hearing aids have special anti-feedback circuitry to prevent (or greatly reduce) feedback.

Frequency

The number of vibrations per cycle/second in a sound wave. Typically referred to as a Hertz (Hz).

Frequency modulation system (FM)

A wireless assistive listening device that picks up a speaker's voice through a microphone and transmits it, using radio waves, to a person wearing a corresponding FM receiver. The device effectively moves the speaker's mouth right up to the hard of hearing person's ears thus removing background noise and distance problems

G

Gain

An increase in the amplitude or energy of an electrical signal with amplification. Gain is the difference in amplitude between the input signal and the output signal.

H

Hair cells

Sensory cells in the inner ear where nerve endings attach to the auditory or vestibular nerves. Hair cells within the cochlea convert sound waves into electrical (nerve) impulses that are carried by the brain.

Hearing aid

A device that amplifies sound and directs it into the ear canal. A hearing aid usually consists of a microphone, amplifier and receiver. Hearing aids come in 4 basic styles: In the ear (ITE), behind the ear (BTE), body aid and eyeglass hearing aid. Body aids are seldom used except for profound losses. Eyeglass hearing aids had their heyday in the 1960s and 1970s. They are not used today. cells in the vestibular labyrinth respond to motion.
Hearing aid evaluation:  The process of selecting an appropriate hearing aid. The audiologist will evaluate different types of hearing aids to determine which is best suited to a particular hearing loss.

Hearing aid trial

A period of time (usually 30 days) during which a person may try hearing aids that were custom made for them. If unsatisfied for any reason, the person should be able to return them for a refund (minus an agreed upon trial fee.

Hearing in noise test (HINT)

A hearing test (usually used in testing people with hearing aids and cochlear implants) in which sentences are spoken against a background of white noise.

Hearing loss

The loss of hearing ability characterized by decreased sensitivity to sound in comparison to normal hearing. Hearing loss may be conductive, sensorineural, or mixed. Hearing loss ranges from slight to profound. Typically the classes of hearing loss are based on the average hearing loss at 500 Hz, 1000 Hz and 2000 Hz.

Here is one commonly used classification:

• Normal hearing:  -10 to 15 dB
• Slight loss:  16 to 25 dB
• Mild loss:  26 to 40 dB
• Moderate loss:  41 to 55 dB
• Moderately severe loss:  56 to 70 dB
• Severe loss:  71 to 90 dB
• Profound loss:  91 to 120 dB

Hearing threshold

The quietest level a person can hear at least 50% of the time under ideal conditions.

Hertz

The frequency or pitch of a sound in cycles per second. It is abbreviated as Hz. It was named after the German physicist Heinrich Rudolf Hertz.

Hyperacusis

Abnormal hearing sensitivity. Some times described as "noise intolerance." If you have hyperacusis, you now perceive sound of normal volume as much too loud. In fact, your may perceive them as being painfully loud. Hyperacusis can be caused by exposure to loud sounds, or as a result of taking certain drugs.

I

Impedance measurements

A physical measurement of a sound reflected off the eardrum and analyzed to reveal characteristics of the middle ear. (See also Tympanometry and Tympanogram.)

Individualized education program (IEP)

A team-developed written document developed with input from the child's parents, the child (when appropriate), teachers, school administrators and special service providers. The IEP refers to the formal educational plan that is developed for each child who receives special services through a local school district. It outlines the goals for education and therapy for a student with a disability, and provides a guideline for achieving them. An IEP for a hard of hearing child should take into consideration such factors as:

• The communication needs of the child, and the family's preferred mode of communication 
• Linguistic needs
• Severity of the hearing loss and the potential for maximizing auditory ability
• Academic level
• Social and emotional needs, including opportunities for peer interactions and communication

Individualized family service plan (IFSP)

A team-developed written plan for providing early intervention and other services to eligible infants and toddlers (aged 0 to 3 years) and there families which addresses:

• Assessments of the child's strengths and needs, and identification of services to meet such needs
• Assessments of family resources and priorities, and the identification of supports and services necessary to enhance the capacity of the family to meet the developmental needs of the infant or toddler with a disability
• A written individualized family service plan developed by three members of a multidisciplinary team including the parent or guardian.

Individuals with Disabilities Education Act (IDEA)

The individuals with disabilities in education Act PL94-142, revised.

Infrared system

A kind of assistive listening device that transmits amplified sound by light waves to a receiver, thus eliminating background noise and distance problems.

Inner ear

The third (innermost) section of the ear where sound vibrations and balance signals are transformed into nerve impulses. The inner ear contains the cochlea (organ of hearing) and the labyrinth or vestibular system (the organ of balance).

Internal feedback

A whistling or squealing that results when sound that is supposed to go into the ear  goes instead directly to the microphone through a damaged hearing aid case and becomes amplified again and again. Internal feedback can also be due to an electronic fault in a hearing aid. In contrast, external feedback is the result of the ear mold not fitting tightly and allowing sound to escape from the ear canal and reach the microphone.

Interpreter

A person who conveys the spoken message to a person with hearing loss by the use of sign language (visible movements of hands, body and face), orally (silently mouthing the words) or with Cued speech. Sign language interpreters are by far the most common.

In-the-canal hearing aid (ITC)

A type of hearing aid that fits partly in the ear canal but extends to the bowl of the ear

L

Localization

The ability to determine the source or direction of a sound.

M

Mainstreaming

The concept that students with disabilities should be integrated with their non-disabled peers to the maximum extent possible, when appropriate to the needs of the student with the disability. This concept means that hard of hearing and Deaf children should go to regular schools rather than to special schools for the Deaf.

Map

The program stored in the speech processor of a cochlear implant that tells the system how to process sound on each channel so that it is most audible and comfortable for the individual user. Each implant user's map varies considerably from every other user. Maps also change over time.

Masking

Any sound that serves to cover up another. In regards to hearing aids, it usually refers to background sounds covering up what a person wants to hear, or to the sound coming from the hearing aid helping to cover up a person's tinnitus.

Meniere's disease

A syndrome that consists of vertigo, tinnitus, a feeling of fullness in the affected ear and a fluctuating hearing loss. It is thought to be caused by fluid imbalance in the inner ear.

Meningitis

A bacterial or viral inflammation that can cause auditory disorders due to infection or inflammation of the inner ear or auditory nerve.

Middle ear

An air-filled cavity, about the size of a pea, between the eardrum and inner ear containing three tiny bones (called ossicles)—malleus (hammer), incus (anvil) and stapes (stirrup)—that conduct sound from the eardrum to the inner ear via the oval window.

Middle Ear Implants (MEI)

A device is planted into the middle ear through surgery. The implant works in conjunction with an external case that can be worn behind the ear or sometimes in the ear. The process works by vibrating the bones in the middle ear. MEI implants work well because they keep the ear canal and ear unblocked. MEI candidates can have a mild to profound loss of sensorineural hearing.

Mixed Hearing Loss

Type of hearing loss encompassing both Conductive and Sensorineural hearing loss.

Monaural

Referring to just one ear, as opposed to binaural − both ears

Most comfortable loudness level (MCL)

The volume at which sounds are most comfortable for a hearing aid user.

Myringotomy

A small incision made in the eardrum by a physician to equalize air pressure and/or to drain infection or fluid from the middle ear.

N

Neckloop

A loop of wire worn like a necklace that creates a magnetic field that can transmit sound when plugged into a portable radio or personal ALD such as an FM or Infrared receiver.

Neurologist

A medical doctor whose specialty is problems of the peripheral and central nervous systems, and their connection to the senses.

Nystagmus

Involuntary, rapid, rhythmic, back-and-forth movement of the eyes that may accompany vertigo. This is typically caused by damage to the vestibular system, or to the central nervous system.

O

Occlusion effect

A change in the acoustical properties of the ear that results from the physical presence of a hearing aid in the ear canal. The result is that the fells like they are talking inside a barrel. Some modern hearing aids can largely overcome the occlusion effect.

Oral deaf education

An approach based on the principle that most hard of hearing and deaf people can be taught to listen and speak with early intervention and consistent training to develop their hearing potential. The goal is for these children to grow up to become independent, participating citizens in mainstream society. Also known as Auditory-oral education.

Otitis externa

Infection (inflammation) of the outer part of the ear extending into the ear canal. It may be accompanied by pain, swelling and secretions. Sometimes referred to as "swimmer's ear."

Otitis media

Inflammation of the tissue lining the middle-ear cavity. Often resulting in infection (fluid) in the middle ear. It occurs when the Eustachian tube becomes blocked and the fluid that builds up in the middle ear becomes infected. Usually results in a temporary conductive hearing loss. Common in children. Children with recurrent attacks may have fluctuating hearing loss and may be more at risk for acquiring permanent hearing loss.

Otitis media with effusion (OME)

Inflammation of the middle ear with an accumulation of fluid behind the eardrum in the middle ear space.

Otoacoustic emissions (OAE)

Inaudible, but measurable, sounds created by the vibrations of hair cells in the cochlea, which bend with the movement of fluid. OAEs are measured with a sensitive microphone placed in the ear canal. OAEs are used by audiologists as a test of inner ear (cochlear) function.

Otitis externa

Infection (inflammation) of the outer part of the ear extending into the ear canal. It may be accompanied by pain, swelling and secretions. Sometimes referred to as "swimmer's ear."

Otitis media

Inflammation of the tissue lining the middle-ear cavity. Often resulting in infection (fluid) in the middle ear. It occurs when the Eustachian tube becomes blocked and the fluid that builds up in the middle ear becomes infected. Usually results in a temporary conductive hearing loss. Common in children. Children with recurrent attacks may have fluctuating hearing loss and may be more at risk for acquiring permanent hearing loss.

Otitis media with effusion (OME)

Inflammation of the middle ear with an accumulation of fluid behind the eardrum in the middle ear space.

Otoacoustic emissions (OAE)

Inaudible, but measurable, sounds created by the vibrations of hair cells in the cochlea, which bend with the movement of fluid. OAEs are measured with a sensitive microphone placed in the ear canal. OAEs are used by audiologists as a test of inner ear (cochlear) function.

Otologist

(oh-TALL-oh-jist) An otolaryngologist who has completed a specialty fellowship focused on ear disorders. Otologists complete over 10 years of medical training and a specialized otology training fellowship prior to entering practice.

Otosclerosis

(OH-toe-sklair-ROW-sis) An inherited dominant genetic condition that causes abnormal spongy bone growth on the tiny bones in the middle ear and in the bone surrounding the oval window. Often this results in the stirrup (stapes) becoming fixed to the oval window of the cochlea, Because the stapes no longer vibrates freely, this causes a progressive conductive hearing loss. If the otosclerosis eventually invades the cochlea (cochlear otosclerosis), the result is additional (sensorineural) hearing loss.

Ototoxic

(oh-toe-TOX-ick) Refers to any chemical or medication (drug) that is potentially harmful to the auditory system—especially to the cochlear and vestibular organs and associated nerves—concerned with hearing and balance. Ototoxic medications may aggravate an existing hearing problem or cause new hearing problems. For a more in-depth understanding of ototoxic drugs, read this article.

P

Phoneme

The smallest unit in a language that is capable of conveying a change in meaning. For example, the "m" in "mat" and the "b" in "bat." There are 41 phonemes in the English language.

Pidgin signed English (PSE)

A form of signing that uses American Sign Language signs for the most part, but signed in English word order. People that are hard of hearing, if they sign, generally use PSE to supplement their oral communication.

Postlingually deafened

Deafness (hearing loss) that occurs after language has been acquired.

Posturography

A test that measures how you maintain your balance when one or more of your senses is blocked.

Pre-lingually deafened

A person who is either born deaf or who lost his hearing early in childhood, before acquiring language.

Presbycusis

(prez-bee-KOO-sis) Gradual hearing loss, especially in the high frequencies, due to aging.

Pressure equalization tube (PE)

A small tube that is surgically inserted in the eardrum to equalize the pressure between the middle ear and the ear canal and to permit drainage. PE tubes are used when a Eustachian tube is not working properly or is clogged up.

Proprioceptive system

(proh-pree-oh-SEP-tiv) One of the three separate balance systems in your body. It consists of nerve sensors in the muscles, tendons and joints, especially in your legs, ankles and feet, that help you to keep your balance. The other two systems are your visual system and your vestibular system in your inner ears. When you vestibular system is damaged, your proprioceptive system works with your visual system to give you some semblance of balance.

Pure tone air conduction audiometry

Measurement of hearing thresholds to pure tones presented through earphones or ear inserts.

Pure tone average (PTA)

The average of your hearing loss at the following 4 test frequencies—500, 1,000, 2,000 & 4,000 Hz. The PTA is expressed in decibels (dB).
Pure tone bone conduction audiometry:  Measurement of hearing thresholds to pure tones presented from a small vibrator placed against the skull.

R

Real ear measurement

A testing technique used to measure the sound levels produced by a hearing aid while in the are canal. A tiny probe microphone is placed in the ear canal ahead of the hearing aid. Real ear measurement  evaluates how well a hearing aid is producing the amplification and quality of sound it should when it is actually working in the ear canal.

Receptive language

Understanding language. This includes memory and understanding what is heard (or seen in the case of sign language). Therefore, receptive language relies on hearing or seeing

Recruitment

(re-KROOT-ment) The abnormally greater increase in the sensation of loudness in response to increased sound intensity as compared with a normal ear. In practical terms, if you have recruitment, you perceive certain louder sounds as much louder than normal, and they often hurt. Recruitment is one result of the greatly-reduced dynamic range found in people with sensorineural hearing losses.

Residual hearing

The amount of measurable, usable hearing left to a person with a hearing loss.

S

Sensorineural Hearing Loss

A type of hearing impairment caused by damage that occurs to the cochlea. Sensorineural damage is usually irreversible.

Signal-to-noise ratio

The relationship of a primary signal (a person talking) to the level of the ambient background noise. People with hearing loss need a much better signal-to-noise ratio than people with normal hearing.

Signed English

A form of sign language that uses signs in English word order, often with added suffixes and prefixes that are not present in American Sign Language. Signing Exact English and Seeing Essential English are two examples.

Sign language

A manual system of communication by which concepts and language are represented visually through hand movements, gestures and facial expressions rather than spoken words. In the United States and Canada, the most common signed language is American Sign Language (ASL). Most hard of hearing people that learn some sign (not that many do in the first place) typically use signed English (pidgin signed English) to supplement speech when communication becomes difficult.

Sound field system

An FM system that has a small loudspeaker near the listener to amplify the speaker's voice. The speaker wears a wireless FM microphone. Sound field systems used in classrooms may have several loudspeakers focused on different parts of the classroom so all students can hear better.

Speech awareness threshold (SAT)

The lowest hearing level in decibels at which a person can detect the presence of speech. Also knows as the speech detection threshold (SDT).

Speech intelligibility

The ability to be understood when using speech. As hearing loss increases, typically speech intelligibility decreases.

Speech-language pathologist (SLP)

A health care professional (minimum of a Masters degree in Speech-language pathology) whose professional practice includes the evaluation, rehabilitation and prevention of speech and language disorders. Speech and language delays are frequently seen in children with hearing losses.

Speech perception

The ability to recognize speech when it is presented at suprathreshold levels (levels loud enough to be heard).

Speech recognition threshold (SRT)

The faintest level at which a person can understand simple two-syllable words (spondee words) 50% of the time. Also known as the Speech reception threshold (SRT), Speech threshold (ST) or Spondee threshold (ST).

Spondee

A two-syllable word that has equal stress on both syllables. Some examples of spondee words include baseball, cowboy, hotdog, ice cream and railroad. Spondee words are used in Speech Recognition Threshold (SRT) testing.

Syndromic hearing loss

A hearing loss that is accompanied by additional physical characteristics such as blindness, physical deformities or mental retardation. It may also involve other organs.

T

Telecoil

A tiny coil of wire built into many hearing aids that allows the hearing aid to pick up the magnetic fields emitted by  telephones, various assistive listening devices, or induction room loops. Sometimes referred to as "t-switch" or "t-coil."

Threshold

In audiometry, the softest sounds (usually pure tones or speech) a person can detect 50% of the time. The term is used for both speech and pure tone testing.

Tinnitus

(TIN-ih-tus or tih-NIGH-tus) A sensation (subjective perception)  of various (phantom) noises in the ears. Tinnitus is variously described as ringing, roaring, clicking, humming, buzzing, swishing, whooshing, clanging, shrieking and other similar sounds that seems to originate in your ears or head. It is not a disease, but a symptom of various abnormal underlying condition it he auditory system. It is often associated with hearing loss and exposure to loud noise.

Total communication

An approach to communicating with severely and profoundly hard of hearing people that includes simultaneous use of signing and speech (simultaneous communication, or sim-com), sometimes supplemented with written information.

Tympanic membrane

The eardrum. It separates the outer ear from the middle ear and is conducts sound to the middle ear. More technically, the eardrum is a  thin, taut, concave, pearly-white membrane that covers the entrance to the middle ear. It vibrates in response to incoming sounds, which are then transmitted to the middle and inner ear.

Tympanogram

A measure of the mobility of the eardrum. A tympanogram is a graph that shows how well the middle ear pressure regulating system is working, whether the eardrum is intact and how well it moves. It can be used to identify middle ear disorders that require medical attention.

U

Uncomfortable loudness level (UCL)

The volume at which sounds become uncomfortably loud. Any further increase in volume would hurt.

Unilateral hearing loss

Hearing loss in one ear only. Unilateral hearing loss adversely affects the educational process in a significant percentage of students who have it.

V

Vent

A small hole through a In-the Ear hearing aid or earmold to allow air into the ear. The size of the vent can be modified to change the acoustical properties of a hearing aid.

Vertigo

Vertigo is the illusion or sensation of movement when none is present. If may feel like you are spinning around, or that the room is spinning around you. Frequently vertigo is accompanied by feelings of imbalance and/or nausea. Vertigo is a common result of damage to the balance system of the inner ear. Less often, it is caused by abnormal conditions in the central nervous system. Many ototoxic drugs can cause vertigo.

Vestibular system

That portion of the inner ear and the central nervous system involved with the sense of balance. It includes the semi-circular canals, saccule, utricle and vestibule. This system controls your equilibrium (balance) and stabilizes your eyes in space. It works together with your brain to sense, maintain and regain your balance and a sense of where your body and its part are positioned. It regulates movement (walking, running, etc.) and keep objects in visual focus as the body moves. Many ototoxic drugs can damage your vestibular system. This can give rise to a whole host of balance-related problems.

Visual reinforcement audiometry (VRA)

A hearing testing procedure for children in which the child's responses to sound are reinforced with a visual event (such as a toy that moves). The audiologist attempts to condition the child to look for the toy when a sound is heard, thus providing a method for testing the hearing of small children. This procedure is most appropriate for children in the 6-month to 3-year age range

W

Wide dynamic range compression

A special circuit in some hearing aids that compresses a wide range of sounds into a narrower range. This makes soft sounds easier to hear and makes loud sounds more comfortable for listening.

Word recognition testing (WR)

A test that determines how well you can understand single-syllable words when they are heard at your most comfortable level. The results are expressed as a percentage.