Audiometry

Audiometry (synonym of ekometrija) - study acuity of hearing.
Hearing study was most frequently whispered, conversational speech (tables the words of Vojacek) and tuning forks (see). In the study of the hearing of the ear that is not investigate, close your finger or a cotton wool. The distance (in meters), from which the subject distinguishes these or those spoken by the doctor 's words, recorded as hearing acuity to the whispered and spoken speech. The ability to read from the lips of this study should be excluded.
Hearing acuity in pure tones investigated tuning forks. In addition, tuning forks (frequency 128 or 256 fluctuations in 1 sec.) used for additional research.
Weber's Experience. Leg sounding tuning fork put on the crown of the investigated strictly on the middle line. Normally the sound is felt in the heador in both ears with the same intensity. With the defeat of conductive better patient hears the affected ear, diseases zvukooperatora departments - healthy ear.
Experience Rennes. Leg sounding tuning fork put on mastoid investigated. After the sounds of the tuning fork has no effect, it is removed from the mastoid process and bring to your ear. Under normal hearing (positive experience Rennes) in the treatment begins again to hear the sound of a tuning fork, which indicates the normal state of the conductive system.
Shvabakh's Experience. Determine the length of time perception in patients sound tuning fork with the crown and compare it to normal.
Studies hearing instrument - audiometers - give more accurate results. There are tones and speech audiometers. Tone audiometer consists of a generator audio, phones (air and bone) and regulators in the frequency and intensity of the sound. Before audiometry surveyed instructed, put on his ears phone and set the frequency supplied tone. If the audiometry produce sounds of increasing intensity, the controller is pre-set to "0", and then gradually shift increasing the volume. When the signal of the patient, which means that he hears supplied sound, note the value of threshold of perception of sound. In the study of hearing the sound of diminishing in intensity phone serves obviously audible patients sound. Reducing the intensity of the sound, mark the moment when the patient stops to hear it.
For research of bone conduction sound bone telephone applied to the mastoid and densely press his padded headband or hand. The study produced the same way as when defining thresholds air conduction. All measurements hearing calculate in decibels. The results of audiometry fixed on special forms - audiograms. For mass examinations and professional selection use audiometers-testers simplified design.
Speech audiometer allows the study of hearing a speech through a microphone or recorded on phonograph record, as well as on the tape. Hearing status assessed as a percentage of the number of correctly perceived words. The research results depicted in the form of curves of speech intelligibility. As tone and speech audiometry are made in a special soundproof rooms (chambers).
Currently, the term "audiometry" is often used when talking about hearing research using audiometers.

Audiometry (from lat. audio - hear and Greek. metreo - measure; a synonym for ekometrija, from the Greek. akouo - hear - the measurement of the severity of hearing. As the hearing acuity, or the sensitivity of the auditory analyzer, is determined by the threshold of perception of sound, audiometry is reduced mainly to define the threshold of perception of sounds of different frequencies, i.e. to determine the lowest intensity at which it becomes audible.
The easiest and most accessible method of audiometry is the study of hearing speech. For this purpose apply and whispered loud speech. In complete silence whispered speech is perceived with normal hearing at a distance of 20-25 meters In normal conditions of research, i.e. in a situation of relative silence, hearing is normal if the whispered speech is perceived from a distance of 6-7 meters In the absence of perception whispered speech, or a sharp fall pass to the study of hearing loud speech. Initially, apply it to medium, or so-called oral, volume, which is attached to the voice during a normal conversation. If it conversational volume varies subjects with little or no different, apply it enhanced the volume. The study of hearing speech cannot be the sole method of determining the functional capacity of the auditory analyzer, because this method is not objective as the dosage of sound power and outcomes evaluation.
A more accurate method of research of hearing with a tuning-fork. In practice usually apply the tuning forks configured on the tone ("to") in different octaves. For a detailed study of hearing use a complete set, which includes the tuning forks With1, s, 1, 2, 3, 4, 5, respectively giving 32, 64, 128, 256, 512, 1024, 2048 and 4096 fluctuations in 1 sec. The tuning forks denote the corresponding letter and a number indicating the number of oscillations per 1 sec. (64, 128, 256 , and so on). The full set of tuning forks is complemented by a special whistle, which receive the highest sounds (from 4,000 to 20,000 vibrations per 1 sec.). In everyday practice, the hearing research produce more often three forks (128, 512, 2048 or4096) or even two (With128 and with2048).
Using tuning forks, you can explore the hearing acuity as in air and bone conduction. For research of air zvukoprovodnost a sounding tuning fork bring to the investigated ear and define the time interval from the beginning of the sound until the time of his disappearance. Bone conduction explore, pressing the foot sounding tuning fork to the mastoid or to the crown. By comparing the time during which the sound of the tuning fork is perceived investigated by ear, with the duration of the same tuning fork for hearing of the ear and is determined by the acuteness of hearing the sound of this tuning fork. It is advisable to mark the time of the hearing, not in absolute terms (seconds), and the percentage of time perception of the tuning fork healthy ear.
The most advanced method is to study the hearing with the help of electro-acoustic apparatus - audiometer.
After the introduction into practice of audiometers (formerly known as autoaudio) the term "audiometry" were used mainly to refer to studies hearing with the help of this device.
The audiometer is a tube generator variables electrical stresses on the phone turn into sound vibrations. For research of hearing thresholds in the air and bone conduction use special phones - "air" and "bone". The intensity of sound waves may change in a very wide range: from little below the threshold of" hearing, up to 120-125 dB (for sounds of medium frequency). Height published by the audiometer sounds may also vary within a wide range - from 50 to 12 000-15 000 Hz. Sound intensity is determined by the scale of the audiometer, which graduated in decibels usually in relation to normal hearing.
When measuring the severity of hearing using audiometer (Fig. 1)changing the pitch by pressing the appropriate buttons or rotate the drive, and the power of sound by turning the handle of the attenuator (regulator intensity), establish the minimum intensity in which sound is the height becomes barely audible (threshold intensity). Defining the scale of the audiometer threshold intensity hearing of the subject, establish the extent of hearing loss in decibels.
The result of the investigation hearing acuity using audiometer write in an audiogram. On audiometric grid (Fig. 2) put as points readings audiometer for each ear separately; curve connecting these points, called an audiogram. Comparing the position of audiograms obtained and the corresponding normal hearing (represented as a horizontal line passing through zero), you can get a clear picture about the state of auditory function.
Recently began using the so-called speech audiometry. Unlike normal or tone audiometry at which investigated the auditory sensitivity to colours, different heights, when speech A. define the threshold of discernment speech. On the audiometer in this case it is served either directly (through the microphone), or after pre-recording on a magnetic tape.

Fig. 1. Hearing study using the audiometer.
Fig. 2. Audiogram.

The threshold of discernment, or the minimum intensity of the speech, which investigated a Discerner of 50% of words is determined by attenuator and is measured in decibels.
In comparison with other methods of research of hearing acuity using audiometer has a number of advantages: 1) much greater precision of measurement;
2) a significantly higher intensity of the emitted sounds; the maximum power of the sound of the human voice and tuning forks 90 dB, using the same audiometer you can get sound intensity up to 125 dB, which allows to measure very large extent, the decrease in hearing, and in some cases to identify and pain thresholds;
3) the ability to evaluate hearing acuity in common and easily comparable units (decibels); 4) the opportunity to explore the bone conduction for high sounds that are excluded in the study of hearing tuning forks.
For a complete description of the function of the auditory analyzer apply special methods of audiometry: a study of the severity of hearing in terms of sound - the so-called noise A., and also methods of above-threshold A., which include the study of the phenomenon loudness equalization (recruitment), the definition of differential threshold of sound power and others (see Hearing).


The use of tone and speech A. in the study of hearing acuity in young children, especially children with hearing and speech is very difficult, because such children usually do not understand the explanations about the mandatory tasks and ways to respond to sounds and, in addition, they lack the skills of listening to sounds of low intensity. The child in such cases reacts to sound not minimal (threshold) power, and the sound, the intensity of which exceeds, sometimes significantly, the threshold. In this regard, in the study of hearing in children using the methods of so-called objective, or reflex, audiometry. Methods A., which are based on butylbenzylamine reactions (see Auro-palpebralis reflex, Auro-pupillary reflex), was not included into wide practice, because these reactions are fickle and their absence may not be invoked as evidence of the lack of hearing.
Much more important are the methods of the conditioned reflex A.: galvanic skin, blink, motor, with estimated reinforcement. In the study of dermal-galvanic method uses a defensive reaction to the irritation of electric shock, manifested in the change of the electric potentials of the skin; through periodic combination of a sound signal with electric irritation possible to develop a conditioned reflex reaction - changing skin potentials in one sound irritated. At hearing research using blink techniques as unconditioned stimulus applied weak stream of air: when the stream of air flows in the face of a child, there is a defensive reaction in the form of batting eyelids. Combining the action of air with a sound signal, you can get uslovnopatogennah reaction (blinking) on one of the audio irritation. When determining the hearing with a propulsion method with an approximate reinforcement auditory stimulus combined with the display (using filmoscope) series plot of the picture, giving thus the sound stimulus signal is.
The conditioned reflex audiometry is widely used in the examination. With the help develop defensive (electric or blink) reflex can not only learn about the presence of hearing, but also to define precisely its sharpness in each ear.
The reliability and accuracy of the results of audiometry largely depend on the conditions in which it is produced. Of great importance, in particular, has insulation from external noise, and from the effects of various other distractions. To eliminate or at least significantly reduce the masking effect of external noise A. conduct in zvukozapisi cameras. These cameras are two or three are located in one of the other boxes, between the walls of which are air gap or sound-absorbing materials. To monitor the analyzed in the wall of the camera is viewing window.