Figures indicate that one out of seven individuals does not have full hearing and one out of ten hears so poorly that a hearing instrument would help.
Studies (Maastricht report on hearing impairment, 1999) also underline the fact that only a minority "less than 14% in the EU" of those for whom a hearing instrument would be beneficial actually use one.
The degree of hearing loss varies from person to person
Between the two extremes of hearing well and hearing nothing, there are many degrees of impairment. The terms used to describe the degree of hearing loss are mild, moderate, severe and profound. Most hearing losses are mild to moderate.
What does the degree of hearing loss mean?
- Mild hearing loss: unable to hear soft sounds, difficulty understanding speech clearly in noisy environments.
- Moderate hearing loss: unable to hear soft and moderately loud sounds, considerable difficulty understanding speech, particularly with background noise.
- Severe hearing loss: some loud sounds are audible but communication without a hearing instrument is impossible.
- Profound hearing loss: some extremely loud sounds are audible but communication without a hearing instrument is impossible.
A human ear with normal hearing can detect a very wide range of frequencies from 20 Hz to 20,000 Hz. The standard hearing test concentrates only on the range of frequencies relevant for understanding speech: 250 Hz to 8000 Hz.
A hearingcare professional tests hearing in a quiet test environment with a specially calibrated audiometer, using specific procedures. Each ear is tested separately since the extent of any damage may be different in each ear.
The hearing range of the test ear is compared to the normal hearing range. The key observations for the different frequencies are "at what level do I begin to hear the sound" and "at what level does the sound become uncomfortably loud". The result is presented in the form of an audiogram.
The hearingcare professional can explain the meaning of the results and the effect of a particular loss on everyday life and communication, and provide information and guidance on the decision concerning hearing instruments.
Hearing Tests for Children
- Hearing Screening
This is testing which can be carried out at any age. Hearing screening usually shows simply that a child's hearing is not at a normal level. If a child fails a screening test, he / she will be referred for a more detailed assessment. In recent years the importance of hearing screening for infants has been recognized. There is now legislation in many countries recommending that all newborns are screened for hearing loss. When hearing loss is identified early appropriate support measures also can begin sooner.
- Behavioral Hearing Tests
These tests usually require the child to respond to soft sounds in some way (verbally, by picture pointing, raising the hand or through a "game"). These tests can be fun and for infants and toddlers, a head-turn response to a test signal is usually the best and most reliable testing method.
- Auditory Brainstem Response
For newborns or infants and children who cannot reliably perform the behavioral test procedures, other more objective tests, such as Auditory Brainstem Response, can help determine hearing abilities. Clicks or tonal "pips" are sounded in an infant's ears through earphones. The ABR provides information about the function of the auditory pathway to the level of the brainstem. The response to the clicks or tones are recorded, providing an estimate of hearing sensitivity.
- Otoacoustic Emissions
These tests provide a unique way to examine the function of the cochlea. Sounds are sent to the child's ear with a small loudspeaker. A microphone records the response to the sound from the cochlea (known as an emission). This offers valuable information about the sensory hair cells in the cochlea.
- Tympanometry (Acoustic Immittance Testing)
This test helps determine how well the eardrum and middle ear are working. A gentle puff of air is delivered into the child's ear and the amount the eardrum moves in response to change in air pressure is recorded. If the eardrum does not move, for example, it could mean there is fluid behind the eardrum and otitis media with effusion may be present.
