Hearing test
Encyclopedia
A hearing test provides an evaluation of the sensitivity of a person's sense of hearing
and is most often performed by an audiologist using an audiometer
. An audiometer is used to determine a person's hearing sensitivity at different frequencies
. There are other hearing tests as well, e.g. Weber test
and Rinne test
.
. People having their hearing tested will convey that they have heard the tone by either raising a hand or pressing a button. As the test progresses, the audiologist or hearing aid specialist, plots points on a graph where the frequency is on the x-axis and the loudness on the y-axis. Once each frequency of hearing ability is tested and plotted, the points are joined by a line so that one can see at a glance which frequencies are not being heard normally and what degree of hearing loss may be present. Normal hearing at any frequency is a sound pressure
of 20dBSPL or quieter; with worsening hearing as the number increases.
is placed behind the ear, on the mastoid process
. When the patient can no longer feel/hear the vibration, the tuning fork is held in front of the ear; the patient should once more be able to hear a ringing sound. If they cannot, there is conductive hearing loss
in that ear. Additionally, the tuning fork is placed on the forehead. The patient is then asked if the sound is localised in the centre of the head or whether it is louder in either ear. If there is conductive hearing loss, it is likely to be louder in the affected ear; if there is sensorineural hearing loss
, it will be quieter in the affected ear. This test helps the audiologist determine whether the hearing loss is conductive (caused by problems in the outer or middle ear) or sensorineural (caused by problems in the cochlea, the sensory organ of hearing) or neural - caused by a problem in the auditory nerve or auditory pathways/cortex of the brain.
Hearing (sense)
Hearing is the ability to perceive sound by detecting vibrations through an organ such as the ear. It is one of the traditional five senses...
and is most often performed by an audiologist using an audiometer
Audiometer
An audiometer is a machine used for evaluating hearing loss. Audiometers are standard equipment at ENT clinics and in audiology centers. They usually consist of an embedded hardware unit connected to a pair of headphones and a test subject feedback button, sometimes controlled by a standard PC...
. An audiometer is used to determine a person's hearing sensitivity at different frequencies
Audio frequency
An audio frequency or audible frequency is characterized as a periodic vibration whose frequency is audible to the average human...
. There are other hearing tests as well, e.g. Weber test
Weber test
The Weber test is a quick screening test for hearing. It can detect unilateral conductive hearing loss and unilateral sensorineural hearing loss...
and Rinne test
Rinne test
The Rinne test is a hearing test. It compares perception of sounds transmitted by air conduction to those transmitted by bone conduction through the mastoid...
.
Audiometer
An audiometer hearing test is usually administered to a person sitting in a soundproof booth wearing a set of headphones which is connected to an audiometer. Small foam insert earphones placed in the ears may also be used. The audiometer produces tones at specific frequencies and set volume levels to each ear independently. The audiologist or licensed hearing aid specialist plots the loudness, in decibels, on an audiogramAudiogram
An audiogram is a standard way of representing a person's hearing loss . Most audiograms cover the limited range 100 Hz to 8000 Hz which is most important for clear understanding of speech, and they plot the threshold of hearing relative to a standardised curve that represents 'normal'...
. People having their hearing tested will convey that they have heard the tone by either raising a hand or pressing a button. As the test progresses, the audiologist or hearing aid specialist, plots points on a graph where the frequency is on the x-axis and the loudness on the y-axis. Once each frequency of hearing ability is tested and plotted, the points are joined by a line so that one can see at a glance which frequencies are not being heard normally and what degree of hearing loss may be present. Normal hearing at any frequency is a sound pressure
Sound pressure
Sound pressure or acoustic pressure is the local pressure deviation from the ambient atmospheric pressure caused by a sound wave. Sound pressure can be measured using a microphone in air and a hydrophone in water...
of 20dBSPL or quieter; with worsening hearing as the number increases.
Weber and Rinne
A complete hearing evaluation involves several other tests as well. In order to determine what kind of hearing loss is present, a bone conduction hearing test is administered. In this test, a vibrating tuning forkTuning fork
A tuning fork is an acoustic resonator in the form of a two-pronged fork with the prongs formed from a U-shaped bar of elastic metal . It resonates at a specific constant pitch when set vibrating by striking it against a surface or with an object, and emits a pure musical tone after waiting a...
is placed behind the ear, on the mastoid process
Mastoid process
The mastoid process is a conical prominence projecting from the undersurface of the mastoid portion of the temporal bone. It is located just behind the external acoustic meatus, and lateral to the styloid process...
. When the patient can no longer feel/hear the vibration, the tuning fork is held in front of the ear; the patient should once more be able to hear a ringing sound. If they cannot, there is conductive hearing loss
Conductive hearing loss
Conductive hearing loss occurs when there is a problem conducting sound waves anywhere along the route through the outer ear, tympanic membrane , or middle ear ....
in that ear. Additionally, the tuning fork is placed on the forehead. The patient is then asked if the sound is localised in the centre of the head or whether it is louder in either ear. If there is conductive hearing loss, it is likely to be louder in the affected ear; if there is sensorineural hearing loss
Sensorineural hearing loss
Sensorineural hearing loss is a type of hearing loss in which the root cause lies in the vestibulocochlear nerve , the inner ear, or central processing centers of the brain....
, it will be quieter in the affected ear. This test helps the audiologist determine whether the hearing loss is conductive (caused by problems in the outer or middle ear) or sensorineural (caused by problems in the cochlea, the sensory organ of hearing) or neural - caused by a problem in the auditory nerve or auditory pathways/cortex of the brain.
Other
- The audiologist or hearing instrument specialist may also conduct speech tests, wherein the patient repeats the words he or she hears.
- In addition, a test called a tympanogram is generally done. In this test, a small probe is placed in the ear and the air pressure in the ear canal is varied. This test tells the audiologist how well the eardrumEardrumThe eardrum, or tympanic membrane, is a thin membrane that separates the external ear from the middle ear in humans and other tetrapods. Its function is to transmit sound from the air to the ossicles inside the middle ear. The malleus bone bridges the gap between the eardrum and the other ossicles...
and other structures in the middle ear are working. The ear canal volume indicates whether a perforation in the eardrum (tympanic membrane) may be present. The middle ear pressure indicates whether any fluid is present in the middle ear space (also called "glue ear" or "otitis media with effusion"). Compliance measurement indicates how well the eardrum and ossiclesOssiclesThe ossicles are the three smallest bones in the human body. They are contained within the middle ear space and serve to transmit sounds from the air to the fluid-filled labyrinth . The absence of the auditory ossicles would constitute a moderate-to-severe hearing loss...
(the three ear bones) are moving. - The last test the audiologist may perform is an acoustic reflexAcoustic reflexThe acoustic reflex is an involuntary muscle contraction that occurs in the middle ear of mammals in response to high-intensity sound stimuli....
test. In this test a probe is placed in the ear and a loud tone, greater than 70 dBSPL, is produced. The test measures the reflexive contraction of the stapedius muscle, which is important in protecting the ear from loud noises, such as a person's own speech which may be 90dBSPL at the eardrum. This test can be used to estimate the hearing thresholds in patients who are unable to perform normal pure tone audiometry and can also give information about the vestibularVestibular nerveThe vestibular nerve is one of the two branches of the Vestibulocochlear nerve . It goes to the semicircular canals via the vestibular ganglion...
and facial nerveFacial nerveThe facial nerve is the seventh of twelve paired cranial nerves. It emerges from the brainstem between the pons and the medulla, and controls the muscles of facial expression, and functions in the conveyance of taste sensations from the anterior two-thirds of the tongue and oral cavity...
s and indicate if a lesion may be present.