There are many things that can cause hearing impairment. Hearing can be affected by lesions in the outer, middle, or inner ear. The main function of a hearing test or audiometric testing, is to evaluate the hearing function, and if it is impaired, to find the exact location of the problem.
Audiometric testing is a means of measuring the function of hearing. Testing will indicate whether something is amiss with the hearing of the individual and the hearing part of the inner ear. Audiometric testing is most often used as an initial screening process to identify any problem that may be present, thereafter more extensive evaluation is undertaken.
There are three general audiometric tests which are carried out most often.
Audiometry is a formal measurement of hearing. An audiometer is used to take these measurements. Hearing is measured at various frequencies ranging from low to high pitches. The hearing level is then quantified in comparison to â€œnormalâ€ hearing readings in decibels. Higher numbers of decibels are an indication of worse hearing function. A â€œ0â€ score is normal. Readings below â€œ0â€ do occur in people who have better than normal hearing function.
Once hearing loss has been determined, the next step is to evaluate whether the loss is due to mechanical reasons or sensory reasons. This is determined by using a bone vibrator. This device bypasses the mechanical parts of the middle ear. If hearing is better using bone than air, this indicates conductive (mechanical) hearing loss.
There are a number of more minor tests also categorized under audiometry and these include things like the speech test where a list of words is read out to see if the individual can discriminate between the words. Acoustic reflex testing is another more non-subjective method of method of audiometry. Loud sounds are introduced into the ear to see whether the stapedius muscles tightens the stapes. Acoustinc reflexes can also measure whether there is a brainstem dysfunction.
Brainstem Auditory Evoked Responses measure the timing of electric waves from the brainstem in response to clicks in the ear.
Octoacoustic emissions is a process that is suitable for use on newborns and it tests the function of the cochlea. A probe containing a microphone and speaker are inserted into the ear canal. Quiet tones are emitted through the speaker and travel up the ear canal, through the middle ear, and stimulate the hairs on the cochlea. The hairs respond by sending out their own tiny sounds which are picked up by the microphone. If the hairs on the cochlea do not generate these tiny sounds, there is hearing loss evident.
In infants the Behavioral Observation Audiology Tests are used. Various intensities of sounds are introduced to the infant through the use of various noisemakers. The audiologist will observe startle responses and motor reflexes in relation to each changing sound. The sounds produced are not standardized in frequency or intensity and this appears to be the problem posed by these tests.
Visual Reinforcement Audiology Tests are used on toddlers between six months and two years of age. The child sits on a parents lap, while sounds of various intensities are emitted by one of two speakers. If and when the sound is heard by the child, the child will turn towards the direction of the sound and be rewarded with a flashing light or perhaps a stuffed toy, or even images of popular cartoon characters.
Condition Play Audiometry becomes very useful as the child progresses in age. The child may be asked to listen for a sound, when the sound is heard, the child needs to carry out a task such as placing a peg in a board. Earphones may be used by the child for this kind of testing.
Electrophysiological testing is a reliable and non-behavioral method of testing for hearing loss in both infants and children.It is non-invasive and painless and can even be carried out while an infant sleeps.
Auditory Brainstem Response is one such type of electrophysiological testing. Earphones are placed on the child or infant and responses ears and scalp are measured in response to sounds emitted through the earphones. The results are compiled by a computer which formulates the results into waveform. From this the audiometrist is able to assess if there is any problem and they are able to localize the problem anywhere along the path from ear canal to brainstem.
Auditory Steady-State Response Tests also involves the measurement of responses from the scalp to tones at various frequencies.
Accoustic emmitence testing assess how the sound travels from the outer ear to the cochlea inside the ear. One such test is the tympanogram which tests for fluid build up behind the eardrum.
Audiometric testing is a fairly safe procedure which does not come with any contraindications of side effects. There is really no special preparation that needs to take place in readiness for audiometric testing except in the case of ABR and ASSR tests being carried out on a child under sedation. Obviously as with all sedation, no food can be ingested for a few hours prior to the time.
There is no specific after care treatment prescribed as it is not necessary except in the case of sedation.
The only risks involved are not to do with the audiometric testing itself but rather in instances where sedation is required, the side-effects of the sedatives needs to be taken into consideration.
Over all the process is painless, fairly fast, non-invasive, and can lead to a fulfilled life if a problem in caught early on and intervention takes place accordingly. There is no reason to fear audiometric testing. If it is, however a first time taking the test, the process should be explained in detail so that there are no misunderstandings and no fears going into the process.
These kinds of tests are to be carried out regularly, even if no problem is evident. You never know what may be underlying and waiting to rear itâ€™s head. Give your child the best opportunity at normalcy and at developing into an individual who is well-adjusted and confident.