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Audiometry
Last reviewed: 03.07.2025
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This scientific term originated from two different words - audio - I hear (Latin) and metreo - I measure (Greek). Their combination very accurately defines the very essence of this method. Audiometry is a procedure that allows you to assess the level of hearing acuity.
After all, how well we hear is determined by the presence or absence of disturbances in the anatomical structure or biofunctional susceptibility of the auditory analyzer. By determining the sensitivity threshold, the specialist evaluates how well the patient hears.
Hearing audiometry
Simple conversational speech or whispering - an ordinary person with normal hearing hears this, perceiving it as a given. But due to various reasons (as a result of injury, professional activity, illness, congenital defect) some people begin to lose their hearing. To assess the sensitivity of the auditory organ to sounds of different tones, such a testing method as hearing audiometry is used.
This method consists of determining the threshold of sound perception. The advantage of this procedure is that it does not require additional expensive equipment. The main instrument is the doctor's speech apparatus. Audiometers and tuning forks are also used.
The main criterion of the hearing norm is considered to be the perception by the ear of the person being tested of a whisper, the source of which is six meters away. If an audiometer is used in the testing process, the test result is reflected in a special audiogram, which allows the specialist to get an idea of the level of sensitivity of hearing perception and the location of the lesion.
So how do they do audiometry? The procedure is quite simple. The doctor sends a signal of a certain frequency and strength to the ear being tested. Having heard the signal, the patient presses a button; if he/she does not hear, the button is not pressed. This is how the hearing threshold is determined. In the case of computer audiometry, the subject must be asleep. Before this, electrical sensors are attached to his/her head, which record changes in brain waves. A connected computer, through special electrodes, independently monitors the brain's reaction to the sound stimulus, constructing a diagram.
Tonal audiometry
To determine the threshold of sound perception, the doctor tests the patient on a frequency range from 125 to 8000 Hz, determining from what value the person begins to hear normally. Tonal audiometry makes it possible to obtain both the minimum and maximum values (the level of discomfort) that are inherent in a specific person being examined.
Tonal audiometry is performed using medical equipment such as an audiometer. Using headphones connected to the device, a sound signal of a certain tone is sent to the ear of the person being examined. As soon as the patient hears the signal, he presses a button; if the button is not pressed, the doctor increases the signal level. And so on until the person hears it and presses the button. The maximum perception is determined in a similar way - after a certain signal, the patient simply stops pressing the button.
Similar testing can be done for young patients, but in this case, game audiometry is more suitable. The result of this procedure is an audiogram that reflects the real picture of the pathology, expressed in the language of numbers and curves.
Threshold audiometry
This study is conducted using an audiometer. The medical equipment market today can offer a fairly wide selection of this equipment from various manufacturers, slightly different from each other. This device allows you to change the irritating sound signal, from a minimum frequency of 125 Hz and then 250, 500, 750, 1000, 1500, 2000, 3000, 4000, 6000 and 8000 Hz. Some manufacturers have extended this scale to 10,000, 12,000, 16,000, 18,000 and 20,000 Hz. The switching step is usually 67.5 Hz. Threshold audiometry, using such medical equipment, makes it possible to conduct testing using both pure tones and a narrow-focus noise curtain.
Switching of sound indicators starts from 0 dB (the threshold hearing norm) and in 5 dB steps the intensity of the sound load gradually begins to increase, reaching indicators of 110 dB, some models of the device allow you to stop at 120 dB. The latest generation devices make it possible to get a smaller step range of 1 or 2 dB. But each model of the audiometer is equipped with a limitation on the intensity of the output stimulus at three indicators: 125 Hz, 250 Hz and 8000 Hz. There are devices with overhead headphones, represented by two separate air phones, there are also with in-ear phones inserted directly into the auricle. The device also includes a bone vibrator used to analyze bone conduction, as well as a microphone and a button for the patient being examined. A recording device is connected to the equipment, which gives the results of the audiogram test. It is possible to connect playback equipment (tape recorder) used for speech audiometry.
Ideally, the room where the testing takes place should be soundproof. If this is not the case, then when analyzing the audiogram, the audiometrist must make allowance for the fact that external noise can affect the test data. This is usually expressed in an increase in the differentiable sound recognition boundary. At least partially, in-ear phones can solve this problem. Their use allows to increase the accuracy of audiometric studies. Thanks to this device, the general natural noise can be reduced by thirty to forty dB. This type of audiometer fittings has a number of other advantages. With its use, the need for masking sounds decreases, this occurs due to the increase in interaural relaxation to a level of 70-100 dB, increasing the patient's comfort. The use of in-ear phones allows to exclude the possibility of collapse of the external auditory canal. This is especially important when working with small children, namely newborns. Thanks to such equipment, the level of repeatability of the study results increases, which indicates the reliability of the results obtained.
A deviation from the zero mark of no more than 15-20 dB is allowed - this result falls within the norm. Analysis of the air conduction graph makes it possible to assess the level of functioning of the middle ear, while the bone permeability diagram allows you to get an idea of the state of the inner ear.
If a complete hearing loss is diagnosed - deafness - it is difficult to immediately localize the site of damage. To clarify this parameter, suprathreshold tests are additionally carried out. Such clarifying methods include noise studies, Langenbeck or Fowler tests. Such an analysis will help to understand whether the damage concerns the ear labyrinth, the cells of the auditory or vestibular nerve.
Computer audiometry
The most informative and reliable method of research in this area can be called such a procedure as computer audiometry. When conducting this research, using computer equipment, there is no need to actively use the patient being examined. The patient only needs to relax and wait for the procedure to end. Medical equipment will do everything automatically. Due to the high accuracy of diagnostics, low motor activity of the patient and high safety of the method, the use of computer audiometry is allowed in case of need to conduct this research in newborns.
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Speech audiometry
This method of diagnosing hearing level is probably the oldest and the simplest. After all, to determine how a person hears, nothing is needed except for the normal speaking apparatus of the audiometrist. But, as strange as it may sound, the reliability of the study largely depends not only on the condition of the subject's hearing apparatus, the correctness of his perception of the sound signal, but also on his level of intelligence and the breadth of his vocabulary.
Monitoring of this method showed that speech audiometry can show slightly different results if the doctor pronounces individual words or speaks in sentences. In the latter situation, the threshold of perception of the sound signal is better. Therefore, in order for the diagnostics to be more objective and accurate, the audiometrist uses a universal set of simple sentences and words in his work.
Today, this method is practically not used to determine the sensitivity of auditory receptors. But the method has not been forgotten. Speech audiometry in modern medicine has found its application in the selection and testing of a hearing aid for a patient.
Objective audiometry
This method is especially in demand in the forensic field or for determining the threshold of sensitivity in newborns and small children. This is due to the fact that objective audiometry is based on the analysis of conditioned and unconditioned reflexes of the human body, triggered by sound stimuli of varying intensity. The advantages of this method are that the response is recorded regardless of the will of the person being tested.
Unconditioned reflexes of a sound stimulus include:
- The cochlear-pupillary reaction is the dilation of the pupil of the eye.
- Auropalpebral reflex is the closing of the eyelids when suddenly exposed to a sound stimulus.
- Inhibition of sucking reflex in infants at decibels of different tones.
- The blink reflex is a contraction of the orbicularis oculi muscle.
- Galvanic skin response - measuring the electrical conductivity of the body through the skin of the palms of the hands. After sound exposure, this reflex reaction lasts for a long time, gradually fading, and does not present major problems when measuring. Pain exposure is even more persistent. Using pain (cold or any other) and sound stimuli together, the audiologist develops a conditioned galvanic skin response in the patient being tested. This response of the body makes it possible to diagnose the level of the auditory boundary.
- Vascular system response - assessment of the direction and degree of expression of shifts in basic hemodynamic parameters (heart rate and blood pressure). Using plethysmography, an audiometrist can measure the degree of vascular constriction - as a response to a sound of different tones. The measurement must be taken immediately after the sound signal, since this reaction fades very quickly.
Medicine does not stand still and modern scientists, together with doctors, have developed new, more progressive methods and equipment used to determine a person's sound sensitivity, his threshold of perception. Modern methods of objective audiometry include:
- Acoustic impedancemetry is a set of diagnostic procedures that are carried out to assess the condition of the middle ear. It includes two procedures: tympanometry and recording of the acoustic reflex. Tympanometry allows you to simultaneously assess the level of mobility of the eardrum (tympano-ossicular system of the middle ear) and the chain of the bone component of the hearing apparatus (together with muscle and ligament tissues). And also makes it possible to determine the level of counteraction of the air cushion in the tympanic cavity with different dosed micro-oscillations of pumping in the external auditory canal. Acoustic reflex is the registration of a signal from the intra-auricular muscles, mainly the stapedius, as a response to the impact on the eardrum.
- Electrocochleography is a diagnostic procedure for ear diseases performed using artificial electrical stimulation of the auditory nerve, which causes activation of the cochlea.
- Electroencephaloaudiometry, a procedure that records the evoked potential of the auditory area of the brain.
This method of studying the auditory threshold of perception (objective audiometry) is widely used in modern medicine. It is especially in demand in cases where the person being tested cannot (or does not want to) communicate with the audiologist. Such categories of patients include newborns and small children, mentally ill patients, prisoners (during a forensic examination).
Game audiometry
This method is most in demand when communicating with children. It is very difficult for them to sit in one place for a long time and simply press ugly buttons. Much more interesting is a game. Play audiometry is based on the development of a conditioned motor reflex, which is based on the basic movements that the baby uses in his life. The fundamental thing in the method is to interest the little patient not only with a trivial tool (toys and colorful pictures). The audiologist tries to stimulate the baby's motor reflexes, for example, using a switch to turn on a lamp, press a bright button, move beads.
When conducting game audiometry, a specific action, such as pressing a bright key that lights up the screen with a certain picture, is accompanied by a sound signal. Almost all modern methods for determining the threshold of sound sensitivity of the human ear are based on this diagnostic principle.
One of the most frequently used methods is the method developed by Jan Lesak. He suggested using a children's tone audiometer. This device is presented in the form of a children's toy house. The set includes working mobile elements: people, animals, birds, vehicles. This test takes 10-15 minutes at most, so as not to tire the baby too much.
High-precision equipment makes it possible to diagnose the achievement of the hearing threshold quite quickly. The signal is recorded when the corresponding tones and the associated semantic meanings of the game elements are combined. A small person of two or three years old is given a switch in the hands, made in the form of a mushroom. The child is explained that if he presses the key, he, like a superhero, can free various animals and people from captivity. But this can only be done after they ask him to do so. Having heard a squeak (a sound signal emitted by the audiometer's phone), the child must press the key, closing the contact, the animal comes out - this is a signal to the audiometrist that the child has heard the sound of the supplied tone. There is also an option that if the sound is not supplied to the device, and the child presses the key, the animal is not released. Having interested the child and having carried out several control tests, it is possible to obtain a fairly objective picture of the disease with the determination of sound patency in the ear canal and determination of the sensitivity threshold.
The frequency of the tested tones is taken in the range from 64 to 8192 Hz. This method is more acceptable, in contrast to the development of Dix-Hallpike, since testing is carried out in a light room so as not to frighten the baby.
The method of A. P. Kosachev is also used quite actively. It is perfectly adapted for determining the hearing threshold of children aged two to three years. The mobility and compactness of the instruments make it possible to conduct the study in a standard district clinic. The essence of the method is similar to the previous one and is based on the conditioned motor response of the child's body to the electric toys offered to him. At the same time, the set of such toys is multi-set, which allows the audiologist to select exactly the set that will be interesting to a particular child. As a rule, it is possible to develop a reaction in the child to a specific object after 10-15 attempts. As a result, everything (getting to know the child, developing a reaction and conducting the test itself) takes no less than two or three days.
Worthy of attention are the somewhat different, but based on similar reflexology, methods of A. R. Kyangesen, V. I. Lubovsky and L. V. Neiman.
All these developments make it possible to diagnose hearing defects in small children. After all, they do not require speech contact with the child being tested. The whole difficulty of this diagnostics is, first of all, that children with hearing impairments often have a delay in the development of the speech apparatus. As a result, the small patient does not always understand what is wanted from him, ignoring preliminary instructions.
By developing a conditioned reflex response to a sound stimulus in a child, the specialist determines not only the threshold of the child's susceptibility, but also the individual peculiarity of the acquisition of a conditioned motor reflex, the so-called latent period value. The strength of perception, the duration of the child's stable memory for sound stimulation and other characteristics are also established.
Suprathreshold audiometry
To date, many methods have been proposed to determine suprathreshold audiometry. The most widely used is the method developed by Luscher. Thanks to its use, a specialist receives a differential threshold of sound intensity perception, which doctors call the index of small increments of intensity (SII), in international circles this term sounds and is written as the Short Increment Sensitivity Index (SISI). Suprathreshold audiometry leads to a balance of sound intensity, using the Fowler method (if hearing loss affects one side of the hearing aid), and the initial limit of discomfort is recorded.
Structuring of the hearing limit is diagnosed as follows: the subject receives a sound signal with a frequency of 40 dB above the hearing threshold on the telephone. The signal is modulated in the intensity range from 0.2 to 6 dB. The norm for conductive hearing loss is the condition of the human hearing system in which the conductivity of sound waves on the way from the outer ear to the eardrum is impaired, the modulation depth in this case is from 1.0 to 1.5 dB. In the case of cochlear hearing loss (a non-infectious disease of the inner ear), when performing a similar sequence of actions, the level of recognizable modulation decreases significantly and corresponds to a figure of about 0.4 dB. The audiometrist usually conducts repeated studies, gradually increasing the modulation depth.
Suprathreshold audiometry, conducting the Sisi test, begins determining this parameter by setting the device handle to a number 20 dB above the hearing threshold. Gradually, the sound intensity begins to increase. This occurs at intervals of four seconds. Briefly, in 0.2 seconds, there is an increase of 1 dB. The patient being tested is asked to describe his feelings. After this, the percentage of correct answers is determined.
Before testing, having brought the intensity indicators to 3-6 dB, the audiometrist usually explains the essence of the test, only after that the study returns to the starting 1 dB. In a normal state or in the case of a defect in sound permeability, the patient can actually distinguish up to twenty percent increase in the intensity of the sound tone.
Hearing loss caused by a disease of the inner ear, damage to its structures, the vestibulocochlear nerve (sensorineural hearing loss), appears together with a failure in the loudness factor. There were cases when with an increase in the hearing threshold by approximately 40 dB, an increase in the loudness function was observed by two times, i.e. by 100%.
Most often, Fowler's loudness equalization testing is performed if there is a suspicion of the development of Meniere's disease (a disease of the inner ear that causes an increase in the amount of fluid (endolymph) in its cavity) or acoustic neuroma (a benign tumor that progresses from the cells of the vestibular portion of the auditory nerve). Fowler's suprathreshold audiometry is mainly performed when unilateral hearing loss is suspected, but the presence of bilateral partial deafness is not a contraindication to the use of this method, but only if the differential (difference) in the hearing thresholds of both sides is no more than 30-40 dB. The essence of the test is that a sound signal is simultaneously fed to each ear, which corresponds to the threshold value for a given hearing aid. For example, 5 dB to the left and 40 dB to the right ear. After this, the signal coming to the deaf ear is increased by 10 dB, while the intensity on the healthy ear is adjusted so that both signals, as perceived by the patient, are of the same tonality. Then the tone intensity on the affected ear apparatus is increased by another 10 dB, and again the volume is equalized in both ears.
Screening audiometry
An audiometer is a medical device for etholaryngology, currently represented by three types of devices: outpatient, screening and clinical. Each type has its own functional focus and advantages. A screening audiometer is one of the simplest devices, unlike an outpatient device, which gives the audiometrist greater opportunities for research.
Screening audiometry allows tonal diagnostics of the patient's ear hearing state to be performed by air conductivity. The device is mobile and its capabilities allow creating various combinations of sound tone strength and frequency. The research procedure involves both manual and automatic testing. In parallel with testing, the etholaryngological device analyzes the data obtained, determining the level of hearing and sound comfort.
If necessary, the specialist can use a microphone to contact the person being tested; the presence of a connected printer allows you to obtain an audiogram on a hard drive.
Audiometry room
To obtain objective test results, in addition to modern equipment, it is necessary for the audiometry room to meet certain acoustic requirements. After all, monitoring of the procedure has shown that the general external sound background can significantly affect the final test result. Therefore, the audiometry room must be well insulated from external acoustic noise and vibrations. This space must also be protected from magnetic and electrical waves.
This room should be distinguished by a certain freedom, this is especially important for speech audiometry, where a free sound field is required. Analyzing the above, it can be stated that it is quite problematic to meet these requirements in a regular room. Therefore, special acoustic chambers are mainly used for conducting research.
Audiometry booth
The simplest of them are a small booth (similar to a pay phone) with well-insulated walls, in which the person being tested sits. The audiometrist is located outside this space, communicating with the person being tested, if necessary, via a microphone. Such an audiometry booth allows you to muffle the external background by 50 dB or more in the frequency range from 1000 to 3000 Hz. Before putting the booth, permanently installed in the room, into operation, a control test is carried out on a person who obviously has normal hearing. After all, not only the booth itself must be insulated, but the general background of the room in which it is located must be low, otherwise the results of such studies cannot be trusted. Therefore, if the threshold of sound sensitivity of a person with normal hearing is stated to be no higher than 3-5 dB from the norm, you can use such an audiometry booth.
Audiometry standards
The result of the testing is an audiogram tape, which is two signal graphs: one shows the level of hearing acuity of the left ear, the other - the right. There are audiograms that have four curves. Receiving such a printout, the doctor has the opportunity to evaluate not only the sound sensitivity of the auditory receptors, but also to obtain bone conduction. The latter parameter makes it possible to localize the problem.
Let's consider the accepted standards of audiometry, thanks to which a specialist evaluates the degree of susceptibility of auditory receptors, that is, the level of deafness. There is an international classification of this parameter.
- Perception is at a level of 26 to 40 dB - I degree of hearing loss.
- From 41 to 55 dB - II degree of hearing loss.
- From 56 to 70 dB - III degree of hearing loss.
- From 71 to 90 dB - IV degree of hearing loss.
- A reading above 90 dB is complete deafness.
Control points are taken as threshold values for air, defined for frequencies of 0.5 thousand, 1 thousand, 2 thousand and 4 thousand Hz.
The first degree of hearing loss is characterized by the fact that the patient hears normal conversation, but experiences discomfort in a noisy company or if the interlocutor whispers.
If the patient has the second degree, then he can distinguish normal speech within a radius of two to four meters, and a whisper no further than a meter or two. In everyday life, such a person constantly asks to repeat himself.
At the third stage of pathological changes, a person can understand intelligible speech within a radius of no more than a meter or two from himself, and practically does not differentiate a whisper. In such a situation, the interlocutor has to raise his voice even when standing next to the victim.
A patient diagnosed with fourth degree hearing loss can clearly hear words of conversational speech only if his interlocutor speaks very loudly, while being close. In such a situation, it is very difficult to find mutual understanding with the respondent without using gestures or a hearing aid.
If the patient is completely deaf, communication with the outside world without special equipment and aids (for example, exchanging notes) is impossible.
But there is no point in approaching this division unambiguously. After all, the comparison of the audiogram is based on the average arithmetic number that determines the starting level. But in order for the picture to be more informative for a specific case, the forms of audiometric curves should also be assessed. Such diagrams are divided into smoothly descending and ascending, sinusoidal, sharply descending and chaotic forms, which are difficult to attribute to one of the above-mentioned varieties. Based on the configuration of the line, the specialist evaluates the level of unevenness of the fall in sound perception at different frequencies, determining at which of them the patient hears better, and which is not available to him.
Long-term monitoring of audiograms, when conducting audiometry, shows that smoothly descending curves are predominantly observed, maximum deafness occurs at high frequencies. A normal audiogram of a healthy person is a line close to a straight line. It rarely exceeds the values of 15-20 dB.
An important place is also occupied by a comparative analysis of the indicators obtained through the air and through the bone. This comparison allows the doctor to determine the localization of the lesion leading to hearing loss. Based on its data, doctors distinguish three types of pathology:
- Conductive changes, when disturbances in sound permeability are observed.
- Sensorineural defects, when disturbances in sound perception are noted.
- And mixed type.
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Audiometry interpretation
An audiogram consists of two or four graphs plotted on a plane with two axes. The horizontal vector is divided into divisions characterizing the frequency of the tone, determined in hertz. The vertical axis records the level of sound intensity, determined in decibels. This indicator has a relative value, compared with the figure of the accepted average normal threshold of perception, which is taken as a zero value. Mostly, on the diagram, the curve with circles indicates the characteristic of sound perception of the right ear (usually it is red, with the designation AD), and with crosses - the left (mostly this is a blue curve with the designation AS).
International standards specify that air conduction curves are plotted on the audiogram as a solid line, and bone conduction curves as a dotted line.
When analyzing an audiogram, it is worth remembering that the vector axis is located at the top, i.e. the numerical value of the level increases from top to bottom. Therefore, the lower its indicator, the greater the deviation from the norm shown by the graph, and, therefore, the person being examined hears worse.
Decoding audiometry allows the audiologist not only to determine the hearing threshold, but also to localize the location of the pathology, suggesting the disease that caused the decrease in sound perception.
How to cheat audiometry?
Many respondents are interested in how to cheat audiometry? It is worth noting that it is almost impossible to influence the result of computer audiometry, because this process is based on conditioned and unconditioned reflexes of a person. In the case of diagnosis using speech audiometry, when the doctor, having moved away to a certain distance, says test words, and the patient needs to repeat them, in such a situation it is quite possible to simulate poor hearing.