Steadily audible sounds are within a frequency range. Hearing range under ideal conditions
Today we are figuring out how to decipher an audiogram. Svetlana Leonidovna Kovalenko, a doctor of higher education, helps us with this qualification category, chief pediatric audiologist-otorhinolaryngologist of Krasnodar, candidate of medical sciences.
Summary
The article turned out to be large and detailed - in order to understand how to decipher an audiogram, you must first become familiar with the basic terms of audiometry and look at examples. If you don’t have time to read for a long time and understand the details, in the card below - summary articles.
An audiogram is a graph of the patient's hearing sensations. It helps diagnose hearing disorders. The audiogram has two axes: horizontal - frequency (the number of sound vibrations per second, expressed in hertz) and vertical - sound intensity (relative value, expressed in decibels). The audiogram shows bone conduction(sound that reaches the inner ear through the bones of the skull) and air conduction (sound that reaches the inner ear in the usual way - through the outer and middle ear).
During audiometry, the patient is given a signal different frequencies and intensity and mark with dots the amount of minimal sound heard by the patient. Each dot represents the minimum sound intensity at which the patient can hear at a specific frequency. By connecting the dots, we get a graph, or rather, two - one for bone sound conduction, the other for air sound conduction.
The hearing norm is when the graphs lie in the range from 0 to 25 dB. The difference between the bone and air conduction graphs is called the bone-air interval. If the bone conduction graph is normal, and the air conduction graph is below normal (there is a bone-air interval), this is an indicator of conductive hearing loss. If the graph of bone sound conduction repeats the graph of air conduction, and both lie below normal range, this indicates sensorineural hearing loss. If the air-bone interval is clearly defined, and both graphs show disturbances, it means mixed hearing loss.
Basic concepts of audiometry
To understand how to decipher an audiogram, let’s first look at some terms and the audiometry technique itself.
Sound has two main physical characteristics: intensity and frequency.
Sound intensity is determined by the strength of sound pressure, which is very variable in humans. Therefore, for convenience, it is customary to use relative values, such as decibels (dB) is a decimal logarithmic scale.
The frequency of a tone is estimated by the number of sound vibrations per second and is expressed in hertz (Hz). Conventionally, the range of sound frequencies is divided into low - below 500 Hz, medium (speech) 500-4000 Hz and high - 4000 Hz and above.
Audiometry is the measurement of hearing acuity. This technique is subjective and requires feedback from the patient. The examiner (the one who conducts the research) uses an audiometer to give a signal, and the subject (whose hearing is being examined) lets him know whether he hears this sound or not. Most often, he presses a button to do this, less often he raises his hand or nods, and children put toys in a basket.
There are various types audiometry: tone threshold, suprathreshold and speech. In practice, the most commonly used is pure-tone threshold audiometry, which determines the minimum hearing threshold (the quietest sound a person can hear, measured in decibels (dB)) at different frequencies(usually in the range of 125 Hz - 8000 Hz, less often up to 12,500 and even up to 20,000 Hz). These data are noted on a special form.
An audiogram is a graph of the patient's hearing sensations. These sensations can depend both on the person himself, his general condition, arterial and intracranial pressure, moods, etc., and from external factors- atmospheric phenomena, noise in the room, distractions, etc.
How to build an audiogram graph
For each ear, air conduction (via headphones) and bone conduction (via a bone vibrator placed behind the ear) are measured separately.
Air conduction- this is the patient’s hearing directly, and bone conduction is the human hearing, excluding the sound conducting system (outer and middle ear), it is also called the reserve of the cochlea (inner ear).
Bone conduction due to the fact that the bones of the skull capture sound vibrations that enter the inner ear. Thus, if there is an obstruction in the outer and middle ear (any pathological conditions), then the sound wave reaches the cochlea through bone conduction.
Audiogram form
On the audiogram form, most often the right and left ear depicted separately and signed (most often right ear on the left, and the left ear on the right), as in Figures 2 and 3. Sometimes both ears are marked on the same form, they are distinguished either by color (the right ear is always red, and the left is always blue) or by symbols (the right is a circle or square (0-- -0---0), and the left one - with a cross (x---x---x)). Air conduction is always marked with a solid line, and bone conduction with a broken line.
Vertically, the hearing level (stimulus intensity) is noted in decibels (dB) in steps of 5 or 10 dB, from top to bottom, starting from −5 or −10, and ending with 100 dB, less often 110 dB, 120 dB. Frequencies are marked horizontally, from left to right, starting from 125 Hz, then 250 Hz, 500 Hz, 1000 Hz (1 kHz), 2000 Hz (2 kHz), 4000 Hz (4 kHz), 6000 Hz (6 kHz), 8000 Hz (8 kHz), etc., can there may be some variations. At each frequency, the hearing level is noted in decibels, then the dots are connected to create a graph. The higher the graph, the better the hearing.
How to decipher an audiogram
When examining a patient, it is first necessary to determine the topic (level) of the lesion and the degree of hearing impairment. Properly performed audiometry answers both of these questions.
Hearing pathology can be at the level of sound wave conduction (the outer and middle ear are responsible for this mechanism); such hearing loss is called conductive or conductive; at the level of the inner ear (receptive apparatus of the cochlea), this hearing loss is sensorineural (neurosensory), sometimes there is a combined lesion, such hearing loss is called mixed. Disturbances at the level of the auditory pathways and the cerebral cortex are extremely rare, and then they speak of retrocochlear hearing loss.
Audiograms (graphs) can be ascending (most often with conductive hearing loss), descending (usually with sensorineural hearing loss), horizontal (flat), as well as another configuration. The space between the bone conduction graph and the air conduction graph is the bone-air interval. It is used to determine what type of hearing loss we are dealing with: sensorineural, conductive or mixed.
If the audiogram graph lies in the range from 0 to 25 dB for all frequencies tested, then the person is considered to have normal hearing. If the audiogram graph goes lower, then this is a pathology. The severity of the pathology is determined by the degree of hearing loss. There are various calculations degree of hearing loss. However, most widespread received an international classification of hearing loss, which calculates the arithmetic mean hearing loss at 4 main frequencies (the most important for speech perception): 500 Hz, 1000 Hz, 2000 Hz and 4000 Hz.
1 degree of hearing loss— violation within 26−40 dB,
2nd degree - violation in the range of 41−55 dB,
3rd degree - violation 56−70 dB,
4th degree - 71-90 dB and over 91 dB - zone of deafness.
Degree 1 is defined as mild, 2 is moderate, 3 and 4 are severe, and deafness is extremely severe.
If bone sound conduction is normal (0−25 dB), and air conduction is impaired, this is an indicator conductive hearing loss. In cases where both bone and air sound conduction are impaired, but there is a bone-air interval, the patient mixed type hearing loss(disturbances in both the middle and inner ear). If bone sound conduction repeats air conduction, then this sensorineural hearing loss. However, when determining bone sound conduction, it is necessary to remember that low frequencies (125 Hz, 250 Hz) give the effect of vibration and the subject may mistake this sensation for auditory. Therefore, one must be critical of the air-bone interval at these frequencies, especially when severe degrees hearing loss (3-4 degrees and deafness).
Conductive hearing loss is rarely severe, most often grade 1-2 hearing loss. Exceptions include chronic inflammatory diseases middle ear, after surgical interventions on the middle ear, etc., congenital anomalies development of the outer and middle ear (microotia, atresia of the external auditory canals, etc.), as well as with otosclerosis.
Figure 1 is an example of a normal audiogram: air and bone conduction within 25 dB over the entire range of frequencies studied on both sides.
Figures 2 and 3 show typical examples of conductive hearing loss: bone sound conduction is within normal limits (0−25 dB), but air conduction is impaired, there is a bone-air interval.
Rice. 2. Audiogram of a patient with bilateral conductive hearing loss.
To calculate the degree of hearing loss, add up 4 values - sound intensity at 500, 1000, 2000 and 4000 Hz and divide by 4 to get the arithmetic average. We get on the right: at 500Hz - 40dB, 1000Hz - 40dB, 2000Hz - 40dB, 4000Hz - 45dB, in total - 165 dB. Divide by 4 equals 41.25 dB. According to international classification, this is degree 2 hearing loss. We determine the hearing loss on the left: 500Hz - 40dB, 1000Hz - 40 dB, 2000Hz - 40 dB, 4000Hz - 30dB = 150, dividing by 4, we get 37.5 dB, which corresponds to 1 degree of hearing loss. Based on this audiogram, the following conclusion can be made: bilateral conductive hearing loss on the right, 2nd degree, on the left, 1st degree.
Rice. 3. Audiogram of a patient with bilateral conductive hearing loss.
We perform a similar operation for Figure 3. Degree of hearing loss on the right: 40+40+30+20=130; 130:4=32.5, i.e. 1 degree of hearing loss. On the left, respectively: 45+45+40+20=150; 150:4=37.5, which is also 1 degree. Thus, we can draw the following conclusion: bilateral conductive hearing loss of 1 degree.
Examples of sensorineural hearing loss are Figures 4 and 5. They show that bone conduction follows air conduction. Moreover, in Figure 4, the hearing in the right ear is normal (within 25 dB), and on the left there is sensorineural hearing loss, with a predominant lesion of high frequencies.
Rice. 4. Audiogram of a patient with sensorineural hearing loss on the left, the right ear is normal.
We calculate the degree of hearing loss for the left ear: 20+30+40+55=145; 145:4=36.25, which corresponds to 1 degree of hearing loss. Conclusion: left-sided sensorineural hearing loss of 1st degree.
Rice. 5. Audiogram of a patient with bilateral sensorineural hearing loss.
For this audiogram, the absence of bone conduction left. This is explained by the limitations of the devices (the maximum intensity of the bone vibrator is 45−70 dB). We calculate the degree of hearing loss: on the right: 20+25+40+50=135; 135:4=33.75, which corresponds to 1 degree of hearing loss; left - 90+90+95+100=375; 375:4=93.75, which corresponds to deafness. Conclusion: bilateral sensorineural hearing loss of the 1st degree on the right, deafness on the left.
Audiogram at mixed hearing loss shown in Figure 6.
Figure 6. There are disturbances in both air and bone sound conduction. The air-bone interval is clearly defined.
The degree of hearing loss is calculated according to the international classification, which is an arithmetic mean value of 31.25 dB for the right ear, and 36.25 dB for the left ear, which corresponds to 1 degree of hearing loss. Conclusion: bilateral hearing loss of 1st degree of mixed type.
They did an audiogram. What then?
In conclusion, it should be noted that audiometry is not the only method for studying hearing. Typically, to establish final diagnosis a comprehensive audiological examination is required, which, in addition to audiometry, includes acoustic impedanceometry, otoacoustic emission, auditory evoked potentials, hearing testing using whispering and colloquial speech. Also, in some cases, an audiological examination must be supplemented with other research methods, as well as with the involvement of specialists in related specialties.
After diagnosing hearing disorders, it is necessary to resolve issues of treatment, prevention and rehabilitation of patients with hearing loss.
The most promising treatment is for conductive hearing loss. The choice of treatment direction: medication, physiotherapy or surgery is determined by the attending physician. In the case of sensorineural hearing loss, improvement or restoration of hearing is possible only in its acute form (with a duration of hearing loss of no more than 1 month).
In cases of persistent irreversible hearing loss, the doctor determines rehabilitation methods: hearing aids or cochlear implantation. Such patients should be observed by an audiologist at least 2 times a year, and in order to prevent further progression of hearing loss, receive courses of drug treatment.
Hearing is the body's ability to perceive and distinguish sound vibrations. This ability is carried out by the auditory (sound) analyzer. That. Hearing is the process by which the ear converts sound vibrations in the external environment into nerve impulses that are transmitted to the brain, where they are interpreted as sounds. Sounds are born from various vibrations, for example, if you pluck a guitar string, pulses of vibrational pressure of air molecules will arise, better known as sound waves.
The ear can distinguish various subjective aspects of sound, such as its volume and pitch, by detecting and analyzing various physical characteristics of the waves.
The outer ear directs sound waves from external environment To eardrum. The pinna, the visible part of the outer ear, collects sound waves into ear canal. So that the sound is transmitted to the central nervous system, sound energy undergoes three transformations. Firstly, air vibrations are converted into vibrations of the eardrum and ossicles of the middle ear. These, in turn, transmit vibrations to the fluid inside the cochlea. Finally, fluid vibrations create traveling waves along the basilar membrane, which stimulate the hair cells of the organ of Corti. These cells convert sound vibrations into nerve impulses in the fibers of the cochlear (auditory) nerve, which transmits them to the brain, from which they are transmitted, after significant processing, to the primary auditory area of the cerebral cortex, the terminal auditory brain center. Only when nerve impulses reach this area does a person hear sound.
When the eardrum absorbs sound waves, it central part, vibrates like a rigid cone, bending in and out. The greater the strength of the sound waves, the greater the deflection of the membrane and the stronger the sound. The higher the frequency of the sound, the faster the membrane vibrates and the higher the pitch of the sound.
The range of sounds with an oscillation frequency from 16 to 20,000 Hz is accessible to human hearing. The minimum sound intensity that can cause a barely noticeable sensation of an audible sound is called the hearing threshold. Auditory sensitivity, or hearing acuity, is determined by the threshold value of the auditory sensation: the lower the threshold value, the higher the hearing acuity. As the sound intensity increases, the sensation of sound volume increases, but when the sound intensity reaches a certain value, the increase in volume stops and a feeling of pressure or even pain appears in the ear. The sound strength at which these appear discomfort, called pain threshold, or the threshold of discomfort. Auditory sensitivity is characterized not only by the value of the threshold of auditory sensation, but also by the value of the difference or differential threshold, i.e., the ability to distinguish sounds by strength and height (frequency).
When exposed to sounds, hearing acuity changes. Exposure to strong sounds leads to hearing loss; in quiet conditions, auditory sensitivity quickly (after 10-15 seconds) is restored. This is a physiological adaptation auditory analyzer to the influence of a sound stimulus is called auditory adaptation. One should distinguish from adaptation auditory, which occurs during prolonged exposure to intense sounds and is characterized by a temporary decrease in auditory sensitivity with more long period restoration of normal hearing (several minutes or even hours). Frequent and prolonged irritation auditory organ strong sounds(for example, in noisy industrial conditions) can lead to irreversible hearing loss. To prevent permanent hearing loss, workers in noisy workshops must use special plugs - (see).
Availability paired organ Hearing in humans and animals provides the ability to determine the location of a sound source. This ability is called binaural hearing or ototopics. With unilateral hearing loss, ototopy is sharply impaired.
A specific feature of human hearing is the ability to perceive speech sounds not only as physical phenomena, but also as meaningful units - phonemes. This ability is ensured by the presence in humans auditory center speech located in the left temporal lobe brain When this center is turned off, the perception of tones and noises that make up speech is preserved, but distinguishing them as speech sounds, i.e., understanding speech becomes impossible (see Aphasia, Alalia).
Used for hearing testing various methods. The simplest and most accessible is research using speech. An indicator of hearing acuity is the distance at which certain elements of speech are distinguished. In practice, hearing is considered normal if the whisper is heard at a distance of 6-7 m.
To obtain more accurate data on the state of hearing, research is used using tuning forks (see) and an audiometer (see).
The person is deteriorating, and over time we lose the ability to detect a certain frequency.
Video made by the channel AsapSCIENCE, is a kind of age-related hearing loss test that will help you find out your hearing limits.
Various sounds are played in the video, starting at 8000 Hz, which means your hearing is not impaired.
The frequency then increases and this indicates the age of your hearing based on when you stop hearing a particular sound.
So if you hear a frequency:
12,000 Hz – you are under 50 years old
15,000 Hz – you are under 40 years old
16,000 Hz – you are under 30 years old
17,000 – 18,000 – you are under 24 years old
19,000 – you are under 20 years old
If you want the test to be more accurate, you should set the video quality to 720p or better yet 1080p, and listen with headphones.
Hearing test (video)
Hearing loss
If you heard all the sounds, you are most likely under 20 years old. Results depend on sensory receptors in your ear called hair cells which become damaged and degenerate over time.
This type of hearing loss is called sensorineural hearing loss. This disorder may be caused by a whole series infections, drugs and autoimmune diseases. The outer hair cells, which are tuned to detect higher frequencies, are usually the first to die, causing the effects of age-related hearing loss, as demonstrated in this video.
Human hearing: interesting facts
1. Among healthy people frequency range that can pick up human ear ranges from 20 (lower than the lowest note on a piano) to 20,000 Hertz (higher than the highest note on a small flute). However, the upper limit of this range decreases steadily with age.
2. People talk to each other at a frequency from 200 to 8000 Hz, and the human ear is most sensitive to a frequency of 1000 – 3500 Hz
3. Sounds that are above the limit of human audibility are called ultrasound, and those below - infrasound.
4. Ours my ears don't stop working even in my sleep, continuing to hear sounds. However, our brain ignores them.
5. Sound travels at 344 meters per second. A sonic boom occurs when an object exceeds the speed of sound. Sound waves in front and behind the object collide and create shock.
6. Ears - self-cleaning organ. Pores in ear canal allocate earwax, and tiny hairs called cilia push wax out of the ear
7. The sound of a baby crying is approximately 115 dB, and it's louder than a car horn.
8. In Africa there is a Maaban tribe who live in such silence that even in old age they hear whispers up to 300 meters away.
9. Level bulldozer sound idling is about 85 dB (decibels), which can cause hearing damage after just one 8-hour day.
10. Sitting in front speakers at a rock concert, you're exposing yourself to 120 dB, which begins to damage your hearing after just 7.5 minutes.
The video made by the AsapSCIENCE channel is a kind of age-related hearing loss test that will help you find out the limits of your hearing.
Various sounds are played in the video, starting at 8000 Hz, which means your hearing is not impaired.
The frequency then increases and this indicates the age of your hearing based on when you stop hearing a particular sound.
So if you hear a frequency:
12,000 Hz – you are under 50 years old
15,000 Hz – you are under 40 years old
16,000 Hz – you are under 30 years old
17 000 – 18 000 – you are under 24 years old
19 000 – you are under 20 years old
If you want the test to be more accurate, you should set the video quality to 720p or better yet 1080p, and listen with headphones.
Hearing test (video)
Hearing loss
If you heard all the sounds, you are most likely under 20 years old. Results depend on sensory receptors in your ear called hair cells which become damaged and degenerate over time.
This type of hearing loss is called sensorineural hearing loss. A variety of infections, medications, and autoimmune diseases can cause this disorder. The outer hair cells, which are tuned to detect higher frequencies, are usually the first to die, causing the effects of age-related hearing loss, as demonstrated in this video.
Human hearing: interesting facts
1. Among healthy people frequency range that the human ear can detect ranges from 20 (lower than the lowest note on a piano) to 20,000 Hertz (higher than the highest note on a small flute). However, the upper limit of this range decreases steadily with age.
2. People talk to each other at a frequency from 200 to 8000 Hz, and the human ear is most sensitive to a frequency of 1000 – 3500 Hz
3. Sounds that are above the limit of human audibility are called ultrasound, and those below - infrasound.
4. Ours my ears don't stop working even in my sleep, continuing to hear sounds. However, our brain ignores them.
5. Sound travels at 344 meters per second. A sonic boom occurs when an object exceeds the speed of sound. Sound waves in front and behind the object collide and create shock.
6. Ears - self-cleaning organ. Pores in the ear canal secrete earwax, and tiny hairs called cilia push the wax out of the ear
7. The sound of a baby crying is approximately 115 dB, and it's louder than a car horn.
8. In Africa there is a Maaban tribe who live in such silence that even in old age they hear whispers up to 300 meters away.
9. Level bulldozer sound idling is about 85 dB (decibels), which can cause hearing damage after just one 8-hour day.
10. Sitting in front speakers at a rock concert, you're exposing yourself to 120 dB, which begins to damage your hearing after just 7.5 minutes.
