Hearing loss, also referred to as hearing loss, is one of the most serious disorders. A high degree of hearing loss makes a person disabled. Congenital hearing loss or acquired in early childhood is especially terrible, because in this case the child is deprived of the opportunity to learn to speak and understand speech.
Fortunately, hearing loss is rarely complete. Even with a hearing loss of up to 90 decibels and above, which is equivalent to deafness, a person still hears something at a very high volume and at certain frequencies. This allows these patients to use hearing aids.
The audiologist should adjust the hearing aid to suit the patient's hearing. To do this, you need to know at what frequencies and at what volume he hears. All this is indicated on a special diagram - an audiogram. It is drawn up in the course of a special diagnostic procedure - audiometry.
For hearing diagnostics, a special device is used - an audiometer.
From the patient's point of view, the procedure is very simple. Headphones are put on it, into which sounds of different frequencies are fed. The volume gradually increases with each sound. When the patient hears a sound, he must press the button. As soon as this happens, the doctor notes the corresponding indicators in the table, which is a coordinate system: horizontally - frequencies in hertz, vertically - loudness in decibels. Sound is delivered alternately to the left and right ears. The points marked in the table are connected in the form of a curve, which gives a complete picture of the patient's hearing.
With audiometry, not only air conduction is diagnosed, but also bone conduction, the results are entered in a separate part of the table.
The main purpose of a hearing aid is to enable a person to understand speech, therefore, the main attention in hearing diagnostics is paid precisely to speech frequencies: 250, 500, 1000, 2000 and 4000 hertz. For these indicators, the arithmetic mean is displayed, this number is an indicator of the average hearing loss.
Other methods for diagnosing hearing
The audiometry method is not always applicable. It is designed for people who understand speech (at least gestural), they can explain what is required of them. This is not possible when it comes to an infant. But it is necessary to diagnose hearing for such children, because the earlier they start wearing hearing aids and study with a deaf teacher, the more successful their speech development will be.
In this case, the diagnosis begins with the registration of otoacoustic emission (OAE) - weak sound vibrations generated by the cochlea. Soft probes are inserted into the child's ears, connected to the apparatus and containing miniature devices - a microphone and a telephone. High-frequency sounds are sent through the microphone in the form of clicks, the phone records the response of the snail. Such a procedure can even be performed on newborns, and in some cases this procedure is sufficient to exclude hearing impairment (for example, when it comes to a premature baby who may not respond to sounds for another reason).
More accurate results are obtained by the method of recording short-latency auditory evoked potentials. Microphones are inserted into the child's ears and electrodes are connected to the head. Sounds of various frequencies and loudness are fed into the microphones, as is done in audiometry, and the reaction of the cerebral cortex is recorded with the help of electrodes. If there is no reaction, then the child does not hear this sound.
Both methods are complemented by tympanometry - a test of the response from the eardrum.
The combination of these methods makes it possible not only to diagnose the patient's hearing state, but also to determine in which department the pathology that caused its decrease occurs: in the middle ear, cochlea, auditory nerve or auditory zone of the brain.