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Audiometry is a medical procedure for measuring the level of human hearing, which is characterized by the completeness of the biofunctional susceptibility of the hearing analyzer in humans and the occurrence of disturbances in the anatomical structure. The term “audiometry” was formed by the merging of two words – the Latin audio (to hear) and the Greek metreo (to measure).
To test your hearing and conduct audiometry, you need to consult an otorhinolaryngologist (ENT doctor), an audiologist.
Principle and features of the procedure
A person with healthy hearing perfectly perceives both colloquial speech and speech that others utter in a whisper. But sometimes such sensitivity can decrease and a person stops hearing quieter speech or a whisper. This is due to injuries, birth defects, professional activities that affect hearing, diseases. To assess the susceptibility of various tones of sounds in medicine, hearing audiometry is used.
The technique of hearing audiometry helps to recognize the threshold of perception of sounds in each individual patient at a certain point in time. The procedure is very simple and does not require sophisticated equipment. All the equipment used in the course of audiometry are tuning forks and audiometers.
The main criterion for the norm of hearing is the ability to recognize a person’s whisper, which is pronounced at a distance of six meters from the ear being examined. When used during the test, an audiometer can identify both the level of hearing sensitivity and the location of the lesion in the body that interferes with the normal functioning of the hearing aid.
Audiometry is very simple. In that auricle, which is currently being examined, an audio signal is given, which is necessary for the doctor to determine the state of frequency and strength. If the patient perceives the signal (that is, hears), he presses the button, if he does not recognize it, then he does not press it. This process perfectly characterizes the threshold of hearing.
When performing computer audiometry, the patient should fall asleep. The day before, special sensors are fixed on his head, which perceive changes in the strength of brain waves. The computer, using special electrodes, helps to independently control all the patient’s brain reactions and build a diagram based on them.
The indications for a hearing test are:
- chronic or acute deafness;
- inflammatory process of the middle ear – otitis media;
- the process of selecting a hearing aid for the patient;
- testing the effectiveness of the therapy.
Audiometry has no contraindications. It can be performed at any time, while the patient does not experience any discomfort or pain. In time, the process takes about half an hour.
There are a lot of varieties of modern audiometry, it can be:
- tonal;
- threshold;
- computer;
- speech;
- objective;
- game;
- suprathreshold;
- screening.
Carrying out tone audiometry
To more accurately measure the patient’s threshold of sound perception, the specialist conducts hearing tests in the range from 125 to 8000 hertz. With tone audiometry, it becomes possible to determine the minimum and maximum sound levels that are comfortable for the person being examined.
An audiometer is used during this procedure, where, with the help of headphones that are connected to the device, a signal of a certain tone is fed into the auricle. If the patient heard the signal, he presses a special button, and if this does not happen, then the tone of the signal increases. This happens until the moment when the signal becomes audible and the patient presses the button. This indicator is the lower limit of the patient’s hearing level. The maximum level is determined exactly according to the same scheme.
Pure tone audiometry can be used for any age of patients, however, a playful form is more suitable for toddlers. As a result of the study, the specialist receives an accurate and complete picture of the patient’s auditory parameters.
Features of the threshold technique
Threshold audiometry is performed using an audiometer. The minimum frequency of the device is 125 hertz, and then it will threshold increase with a run-up of 67,5 hertz to the maximum frequency provided for by a particular audiometer model. A similar procedure is carried out in a soundproof room. If such conditions are not created, then the specialist must take into account the impact of external noise on the test results. To smooth out this imperfection of the procedure, in-the-ear headphones are often used, which can increase the accuracy of studies to identify the level of hearing.
The advantages of in-the-ear headphones are the ability to reduce third-party noise, reduce the need for masking sounds due to inter-aural relaxation, and eliminate the collapse of the external auditory canals. These advantages are of particular importance when working with newborns. The accuracy and regularity of repeating the results suggests that this technique can be considered very reliable. At the same time, analyzing the schedule of individual air permeability, the specialist has the opportunity to draw conclusions about the level of functioning of the middle ear and its condition.
With complete deafness, this technique does not allow you to immediately identify the site of the lesion, to determine it, it is necessary to conduct additional suprathreshold tests. Among such methods, the Fowler or Langenbeck tests, various noise methods are especially popular. Similar types of analyzes will clarify for specialists exactly where the damage is located – in the ear labyrinth, in the cells of the vestibular or auditory nerve.
Use of computer and speech audiometry
Computer audiometry is the most accurate method for determining hearing acuity. Computer equipment provides the patient with complete freedom of action and movement, he can relax and not focus on hearing certain sounds in a timely manner. The equipment itself is able to determine all the limit values, it acts absolutely painlessly and safely, therefore this method is widely used to make an accurate diagnosis even in newborns.
With speech audiometry, on the contrary, all actions are carried out exclusively by the patient and the doctor without the use of any technical means and devices. This is the earliest method for determining the hearing threshold. The result of this procedure can be largely determined not by hearing, but by the intellect and vocabulary of a sick person. Such a technique can give different results when the audiometrist pronounces individual words or arranges them into sentences. Offers are always better perceived by patients and are easier to distinguish.
Modern medicine practically does not use this technique. It is used today exclusively in cases where specialists need to test a patient to choose the right hearing aid for him.
Features of objective audiometry
The objective technique is used in newborns and in the forensic industry. It is based on the analytical features of conditioned and unconditioned reflexes of the human body, which should respond to audio stimuli of different frequencies. The reactions of the body can be recorded with this method for reasons beyond the control of the will of the organism being examined.
Among the unconditioned reflexes that are considered with objective audiometry, one can distinguish dilated eye pupils or a cochlear-pupil reaction, closing eyelids with sudden sounds or an auropalpebral reflex, inhibition of sucking in a newborn with various sounds, contractile ability of the circular eye muscle, galvanic skin changes, reactions vascular system.
Modern objective audiometry is subdivided into acoustic impedancemetry, which includes the process of recording the acoustic reflex, and tympanometry, electrocochleography, and electroencephaloaudiometry. At the same time, tympanometry helps to assess the mobility of the tympanic membranes, the chain of the bone part of the patient’s hearing aid, and with the help of an acoustic reflex, a signal passing from the intra-ear muscles is recorded as a response to the impact on the patient’s tympanic membrane. Electrocochleography allows you to electrically stimulate the auditory nerve, and electroencephaloaudiometry demonstrates to the doctor the potential of the cerebral auditory zone.
Play technique
Play audiometry is mostly used when working with children’s category of patients. Children cannot reflexively press lifeless buttons for a long time, therefore the principle of using game moments is used in the methodology. For example, when a sound is heard and a button is pressed, a small patient will be able to see a new bright picture or some kind of game object, which will stimulate him to follow the commands of an audiologist.
When playing audiometry, a tone audiometer is often used, which was once proposed by specialist Jan Lesak. The audiometer is a toy house with people, animals, vehicles. A small patient is given a remote control in the form of a fungus, with which he will be able to perform certain actions under the right conditions. For example, in order to free a little man from captivity, a small patient must wait until he is asked about it and press the appropriate button on the fungus. So the audiometrist understands that his given signal was heard by the child. A similar technique is proposed by the doctor Kosachev, there are also methods for determining hearing in young patients, tested by other specialists in the industry.
The importance of audiometry in children is expressed in the fact that with a poor level of hearing, babies have a delay in speech development.
Method of suprathreshold audiometry
The suprathreshold method for testing hearing acuity was proposed and tested by Luscher. Thanks to this method, specialists now have the opportunity to evaluate the differential threshold of sound power – the index of small increases in intensity. This study is most often performed if there is a risk of an increase in the volume of lymph in the cavity of the inner ear (Ménière’s disease), auditory neuroma (a benign neoplasm, the source of which is the auditory nerve). The technique of suprathreshold audiometry is used for unilateral hearing loss, however, it can also be used for bilateral anomalies of the hearing aid. In this case, a certain sound signal will be delivered to each ear, which must correspond to the threshold norm of a particular hearing aid. For example, if on one ear the threshold value should be equal to 5 decibels, then on the second, the permissible value may be 40. In this case, the signal that enters the sore ear is gradually increased by 10 decibels, and the boundary sound value supplied on a healthy ear, they are brought into such correspondence that it seems to the patient that a signal of the same intensity is given in both ears. This is how the tone is equalized with a gradual gradation to one threshold equal to 10 decibels.
Application of screening audiometry
A medical audiometer today can be represented by three types of devices – polyclinic, screening or clinical. The simplest device is a screening audiometer, which provides the specialist with a much wider field of possibilities during the procedure than the same outpatient device.
Tone diagnostics of audibility is carried out in this case according to the indicators of sound conductivity of air masses. The screening audiometer is a mobile device, its functionality will allow the specialist to individually select the frequencies and tonality of the sounds produced. It is possible to test the patient in both manual and automatic modes.
During testing, a parallel connected otoscopic instrument will help evaluate the levels of audibility and sound comfort for the patient. With the help of a connected microphone, the doctor has the opportunity to contact the patient, and with the help of a printer, there is a chance to receive an audiogram in printed form.
Cabinet and results of the procedure
In order for the results of audiometry to be objective, the procedure should be carried out in a well-isolated room, where the parallel influence of external noise on the process is minimized. Also, the space where the examination takes place must be protected from electric and magnetic waves.
The room should be free, especially with the speech method, and the distance from the patient to the doctor should be at least 6 meters. The best place for this diagnosis is a specialized acoustic chamber, which is adapted for audiometry.
After the procedure, the specialist receives several special graphics on two-axis planes. On the horizontal axis there are divisions expressed in hertz, and they characterize the frequencies of tones. The vertical axis shows the sound intensity in decibels. The sound perception of the right ear is shown on the red curve, which has circles, and the left ear on the blue curve with crosses.
The solid graphs show air conduction, while the dotted graphs show bone conduction.
Numerical data of hearing levels grow in ascending order on the graphs, which indicates that with a lower indicator of such a value, the maximum deviation from the norm is recorded, that is, the patient in this case hears as badly as possible. Transcribed audiometry charts allow audiologists to determine both hearing thresholds and pathology localization, making diagnoses and prescribing therapy with maximum accuracy.