Hearing aids

Hearing Aids is a complex of research, technical and pedagogical activities aimed at improving auditory function for the social rehabilitation of deaf people and improving their quality of life. This is an individual selection, adjustment of hearing aids and adaptation of the patient to its use.

The hearing aid is a special electronic-acoustic device, which is a kind of artificial limb for the hearing organ intended for amplification of sound. Indications for hearing aids are determined by the degree of hearing loss for sounds related to the speech frequency band (512-4096 Hz). It is established that the range of the most effective use of hearing aids in the intensity calculus is limited by hearing loss in the specified frequency range in the range from 40 to 80 dB. This means that if the hearing loss is less than 40 dB, prosthetics are not shown yet, with hearing loss in the range of 40-80 dB, the use of hearing aids is indicated, and with hearing loss of more than 80 dB, prosthetics are still possible.

Indications for electro-acoustic correction of hearing are determined by a surdologist, individual selection of hearing aids is performed by a technical worker based on those audiometry data that were obtained by examining the patient at a reception at a hearing theologian. These data include information about patients' perception of whisper and colloquial speech, tonal and speech audiograms, if necessary - information on intelligibility and noise immunity of speech, level of auditory discomfort, and others.

Hearing is shown only with bilateral hearing loss, and with asymmetric hearing loss, the hearing aid is applied to a better hearing ear. This achieves maximum effect with minimal amplification of sound, which is of no small importance for more effective adaptation to the use of the apparatus. Very significant is the question of the effect on the hearing of prolonged use of the hearing aid. Among some category of doctors and patients, there is an opinion that using a hearing aid causes deterioration of residual hearing. However, numerous studies and observations have shown that prolonged use of the device not only does not worsen the hearing, but on the contrary, in some cases it improves by 10-15 dB. This phenomenon can be explained by the phenomenon of disinhibition of auditory centers, which is due to the arrival of more intense pulsations with increasing sound.

The best option for hearing aids is binaural hearing, which is especially important in hearing care for children. This is due to the fact that the sound information coming from the right and left ear is processed by the left and right hemispheres respectively, therefore, with bi-inal prosthetics, the prerequisites for the full development of both hemispheres of the brain are created. In addition, with binaural prosthetics, the ototopic function is significantly improved and the need for significant sound enhancement is reduced. Binaural hearing greatly improves the noise immunity of the sound analyzer, the selectivity of the direction of the useful signal, reduces the harmful effect on the hearing organ of high-intensity noise.

Hearing Aids. The history of the use of technical means of amplifying sound to improve hearing with hearing loss is many hundreds (if not thousands) of years. The simplest "device" for improving the perception of the speech of the interlocutor with a deaf person is the palm applied to the auricle in the form of a speaker, which achieves a sound amplification of 5-10 dB. However, such an amplification is enough to improve the intelligibility of speech with a hearing loss of less than 60 dB. The famous Italian scientist Girolamo Gardano, who lived in the sixteenth century, described a method of improving hearing by using a well-dried wooden rod between his teeth, which, while resonating with the surrounding sounds, ensured their entry into the cochlea by bone marrow. Ludwig van Beethoven, suffering from progressive hearing loss, composing musical works, held a wooden rod in his teeth, resting his other end in the piano lid. This actually proves that the composer had a hearing impairment according to the type of sound conducting, which is usually observed in the OS. This fact refutes the legend of the lyuetic origin of the deafness of this greatest composer. In the Beethoven Museum, existing in Bonn, there are numerous acoustic devices made specially for him. This was the beginning of the so-called acoustic means of sound amplification. In subsequent years, numerous acoustic devices were proposed in the form of auditory tubes, horns, horns, etc., which were used to amplify sound both in air and in tissue sound.

A new stage in improving the artificial improvement of the auditory function came in connection with the invention of electrical devices for generating, amplifying and transmitting sound vibrations over a distance by means of wires. This was served by the inventions of A.G. Bell, professor of physiology of the organs of speech of Boston University, the creator of the first electric hearing aid. Since 1900, mass production has begun in both America and Europe. The development of radio electronics led to the creation of amplifiers first on radio tubes, then on semiconductor devices, which ensured the improvement and miniaturization of hearing aids. Much work has been done in the direction of both improving the acoustic characteristics of the hearing aid, and in the field of design. The models of carmaker devices were developed, in the form of hairpins, built-in spectacle frames, etc. The most widespread in Russia were BTE hearing aids, which compensate for almost any hearing loss. These devices differ in size, gain, frequency characteristics, operational controls and various additional functionality, for example, switching the hearing aid to the phone.

Hearing aids are divided into pocket, behind-the-ear, in-the-ear, in-channel and implantable. By the principle of the device - on analog and digital.

Pocket hearing aids are fixed to the patient's clothing. All parts of these devices, except the phone, are located in a separate unit, in which are mounted a microphone, amplifier, frequency filter and battery, as well as controls. Through the connecting cable, the converted, filtered from interference and amplified electrical analogue of the sound is transmitted to the phone, fixed on the insert in the external auditory canal. The constructive solution of the pocket hearing aid, consisting in the fact that the microphone and the phone are spaced apart by tens of centimeters, allows achieving significant sound amplification without the appearance of acoustic feedback, which is manifested by generation (whistling). In addition, this design of the hearing aid allows for binaural hearing, which significantly improves the quality of sound perception, speech intelligibility and returns the function of spatial hearing to the patient. The dimensions of the apparatus allow the introduction into its circuit of additional functions controlled by the corresponding non-operative regulators. In addition to typical pocket hearing aids, hearing aids-glasses, hearing aids-barrettes, etc. Are produced.

BTE hearing aids are the majority of models used by patients. They are small in size, favorably differ from the pocket in cosmetic terms, since they are placed in the behind-the-ear area, often closed with a strand of hair. Their device provides for the placement of all the functional elements of the circuit in one unit, and only a short tube with an olive insert at the end is inserted into the external auditory canal.

In-the-ear and intra-canal hearing aids are optically cosmetic, since the whole structure is located in the initial sections of the external auditory canal and is almost invisible in normal communication with the patient. In these devices, the amplifier with a microphone and a telephone is partially (in-the-ear model) or completely (in-channel model) placed in an individually made-for-impression external ear canal of the earmold, which provides complete isolation of the phone from the microphone and prevents parasitic "stringing".

In modern hearing aids, it is possible to obtain amplification selectively in different areas of the sound spectrum, up to 7.5 kHz, which allows you to raise the signal intensity at frequencies at which there is the greatest loss of hearing and thereby achieve a uniform perception of the sounds of the entire audible frequency spectrum.

Programmable hearing aids. The principle of these devices is based on the availability of a microcircuit, on which several programs for different modes of operation of the hearing aid are recorded: the perception of speech in ordinary domestic conditions or in conditions of extraneous sound interference, telephone conversations,

Digital hearing aids are analogues of mini-computers in which time and spectral analysis of the input signal is carried out, which takes into account the individual characteristics of this form of hearing loss with appropriate adjustment to the input useful and parasitic sound signals. Computer technology makes it possible to significantly expand the ability to control the output signal in terms of intensity and frequency composition even in subminiature intramural models.

Implantable hearing aids. The model of such a device was first used in the USA in 1996. The principle of the device is that the vibrator (analogue of the phone), generating sound vibrations, is strengthened on the anvil and leads it into oscillations corresponding to the input signal, whose sound waves propagate further in its natural way. The vibrator is switched with a miniature radio receiver implanted under the skin into the BTE area. The radio detects radio signals from the transmitter and amplifier, placed outside the receiver. The transmitter is held in the behind-the-go region by a magnet placed on the implanted receiver. By now, completely implantable hearing aids have been developed without any external elements.

Cochlear implantation. This method is the latest development for the rehabilitation of hearing of adults and children with significant hearing loss or deafness (acquired or congenital) by which conventional or vibroacoustic devices no longer help. These patients include those who can not restore airborne sound and inefficient use of bone sounds. Usually these are patients with congenital defect of auditory receptors or with irreversible damage caused by toxic or traumatic lesions. The main condition for the successful use of cochlear implantation is the normal state of the spiral ganglion and auditory nerve, and overlying auditory centers and pathways, including the cortical areas of the sound analyzer.

The principle of cochlear implantation is to stimulate the axons of the auditory (cochlear) nerve by electric current pulses, in which the frequency and amplitude parameters of sound are encoded. The system of cochlear implantation is an electronic device consisting of two parts - external and internal.

The external part includes a microphone, a speech processor, a transmitter of radio-frequency waves containing electromagnetic analogs of sound perceived by a microphone and processed by a speech processor, and a transmitting antenna, a cable connecting the speech processor to the transmitter. A transmitter with a transmitting antenna is mounted in the behind-the-ear area using a magnet mounted on the implant. The implantable part consists of a receiving antenna and a processor-decoder that decodes the received signal, forms weak electrical pulses, distributes them at the appropriate frequencies, and directs into the chain of stimulating electrodes that are inserted during the operation into the cochlear walk. All implant electronics are in a small hermetically sealed body, which is implanted in the temporal bone behind the ear. It does not contain batteries. The energy necessary for its operation comes from the speech processor along the high-frequency path together with the information signal. Contacts of a chain of electrodes are located on a flexible silicone electrode carrier and are located phonotopically in accordance with the spatial position of anatomical structures of CnO. This means that high-frequency electrodes are located at the base of the cochlea, mid-frequency in the middle, and low-frequency electrodes at its apex. In total, such electrodes transmitting electric analogues of different frequency sounds can be from 12 to 22. There is also a reference electrode that serves to close the electrical circuit. It is located behind the ear under the muscle.

Thus, electrical impulses formed by the entire system of cochlear implantation stimulate different sections of the axons of the spiral ganglion, from which the fibers of the cochlear nerve are formed, and, carrying out its natural functions, transmits nerve impulses to the brain along the auditory pathway. The latter takes nerve impulses and interprets them as a sound, forming a sound image. It should be noted that this image differs significantly from the input audio signal, and in order to bring it into line with concepts reflecting the surrounding world, persistent and lengthy pedagogical work is required. Moreover, if the patient suffers from a surdut, then even more labor is needed to teach him an acceptable speech for understanding others.

Technique of hearing aid. In the methodological sense, hearing care is a complex task, requiring strict requirements for the selection of electroacoustic parameters of the hearing aid, adequate to the condition and compensatory possibilities of the patient's residual hearing. Such parameters include, first of all, thresholds of auditory sensitivity in the zone of speech frequencies, levels of uncomfortable and comfortable loudness and dynamic range in the speech frequency zone. Methods of establishing these parameters include psychoacoustic and electrophysiological, each of which has its own methods of quantitative processing, analysis of diagnostic findings. The decisive significance in these conclusions is the calculation of the necessary amplification of the output signal and correction of the hearing loss by frequency. In most of the calculation methods, thresholds of auditory sensitivity and thresholds of comfortable and uncomfortable perception of the signal are used. The basic principle of choosing a hearing aid - according to AI Lopotko (1998) is:

1. for different persons suffering from hearing loss, a different electro-acoustic correction of hearing is necessary;
2. it is necessary to take into account certain relationships between the patient's individual hearing frequency characteristics and the acoustic characteristics of the hearing aid that provide optimal rehabilitation;
3. the amplitude-frequency characteristic of the input gain can not simply be a mirror image of the threshold characteristic of an individual hearing, but must take into account both the psychophysiological features of the perception of sound of different frequencies and intensities (masking phenomena and the FUNG) and the characteristics of the most socially important acoustic signal-speech.

Modern hearing aid provides for a special room equipped with a soundproof camera, voice and speech audiometers, devices for presenting sound signals in the free field, testing and computer tuning of the hearing aid, etc.

As noted by VIPudov (1998), when selecting a hearing aid, in addition to a tone threshold audiogram, thresholds of auditory discomfort are measured, noise immunity of the sound analyzer is examined, the presence of disturbances in loudness functions is detected, and speech audiometry is conducted in a free sound field. Usually, the patient is recommended the type of hearing aid that gives the lowest threshold of 50% of speech intelligibility, the highest percentage of speech intelligibility with the most comfortable perception, the highest threshold of speech perception discomfort and the smallest signal-to-noise ratio.

Contraindications to hearing aid are very limited. These include auditory hyperesthesia, which can serve as a trigger mechanism for various prosopalgia and migraine conditions, a disorder in the function of the vestibular apparatus in the acute stage, acute inflammation of the external and middle ear, exacerbation of chronic purulent inflammation of the middle ear, diseases of the inner ear and auditory nerve, disease.

The question of binaural hearing is decided individually. Monaural prosthetics are performed on the side of better speech intelligibility with a flatter curve (with less hearing loss at higher frequencies), a higher threshold for discomfort perception of speech, which gives the hearing instrument a greater percentage of speech intelligibility at the most comfortable level of its perception. Essential role in improving the quality of perception of the sound signal is played by the design of earmolds (individual production of them).

Primary hearing aid provides for a period of adaptation to the hearing aid, the duration of which is not less than one month. At the end of this period, as appropriate, the parameters of the hearing aid are adjusted accordingly. For young children, hearing aids with a maximum output sound pressure level of not more than 110 dB are used, non-linear distortions of less than 10 dB and a hearing aid's own noise of not more than 30 dB. The frequency band of the hearing aid for children who do not speak is chosen as broad as possible, since for the teaching of speech, complete acoustic information about speech sounds is required. The frequency band for adults can be limited to the limits sufficient to recognize words.

Surdology is a section of otorhinolaryngology that studies the etiology, pathogenesis and clinical picture of various forms of deafness and deafness, developing methods for their diagnosis, treatment, prevention and social rehabilitation of patients. The subject of surdology studies are hearing impairments that have arisen as consequences of inflammatory, toxic, traumatic, occupational, congenital and other diseases of the hearing organ. Deafness is a complete lack of hearing or a degree of depression in which speech perception becomes impossible. Absolute deafness is rare. Usually, there are "rests" of hearing, allowing you to perceive very loud sounds (more than 90 dB), including some sounds of speech, pronounced a loud voice or a cry over your ear. The intelligibility of speech perception in deafness is not achieved even with a loud cry. This deafness differs from hearing loss, in which a sufficient amplification of sound provides the possibility of verbal communication.

The most important surdological method for studying the prevalence of deafness and deafness is screening audiometry among children. According to SL Gavrilenko (1986 - the period of the most effective child-bearing aids in the USSR), 4577 children aged 4 to 14 years were diagnosed with hearing impairment and auditory tube function in 4.7%, with cochleoneusritis at 0 , 85%, adhesive otitis - in 0.55%, chronic purulent otitis media - in 0.28% of children; total - 292 children.

It is also important to conduct audiological events in those secondary technical schools where "noise" specialties are taught. So, according to the Kiev Research Institute of Otolaryngology. AI Kolomiychenko, reflecting the state of auditory function in students of vocational schools on the profile of noise professions, they identified the initial form of perceptive hearing loss. Such persons require special audiological control during their further production activities, as they constitute a risk group for industrial noise hearing loss.

The means of the surdological manual are various methods of investigating the auditory function ("live speech", tuning forks, electroacoustic devices, etc.) and its rehabilitation (medical and physiotherapy, electro-acoustic correction of hearing with the help of individual special hearing aids). The methods of invasive hearing rehabilitation, including the methods of functional otosurgery (miringoplasty, tympanoplasty, fenestration of the ear maze, mobilization of the stapes, stapedoplasty, cochlear implantation) have a direct relation to surdology. The latter is a combination of surgical intervention with the implantation of an electronic analogue of CpO receptors.

Modern methods of hearing research can determine with a high degree of accuracy the total absence or presence of hearing debris, which is of great practical importance for the choice of the method of social rehabilitation of the patient. Significant difficulties arise in the recognition of deafness in young children, since the use of conventional methods (speech, tuning fork, electronic-acoustic) does not reach the goal. In these cases, various methods of "children's" audiometry, for example, sounding toys and various gaming audiovisual tests, are used, based on the visual fixation of spatially separated sound sources or the development of a conditioned reflex to sound when combined with another heteromodal stimulus. In recent years, the registration of evoked auditory potentials, acoustic reflexometry, otoacoustic emission, and some other methods of objective hearing research have become widespread in the diagnosis of hearing impairment in young children.

The appearance of deafness in adults who speak the language leads to a loss of the ability to communicate with others by means of the auditory perception of speech. To these patients, various methods of surdopedagogics are used - reading from the lips, etc. Consequence of deafness congenital or arisen in the dalengial period, when the child has not yet acquired strong speech skills, is dumbness. In appropriate social educational institutions (kindergartens and schools for the deaf and dumb), these children are taught to understand speech through the movements of the speech apparatus of the interlocutor, to speak, to read, to write, to the "language" of gestures.

Pathological processes in the nerve structures of the hearing organ usually lead to persistent disturbances in the auditory function, so treatment of patients with a sensorineural form of deafness and hearing loss is ineffective; only some stabilization of further deterioration of hearing is possible, or some improvement in speech intelligibility and a decrease in ear noise due to improvement of the trophism of auditory centers with the use of drugs that improve microcirculation in the GM, antihypoxants, antioxidants, nootropics, etc. If it occurs as a result of a disturbance in the function of sound transmission, then surgical methods of hearing rehabilitation are used.

Preventive surdological measures in the fight against deafness are:

1. timely detection of nasopharyngeal diseases, disorders of auditory tube functions and their radical treatment;
2. prevention of ear diseases by systematic observation of sick children in infectious hospitals and for healthy children in children's institutions and schools; early and rational treatment of identified diseases;
3. carrying out preventive measures at enterprises with production noise, vibration and other occupational hazards that may affect negatively the function of the auditory analyzer; systematic dispensary observation of persons working in conditions of industrial hazards:
4. prevention of infectious diseases, especially rubella, in pregnant women and timely and most effective treatment of identified diseases;
5. prophylaxis of medicinal, in particular antibiotic, ototoxicoses, their timely detection and treatment, for example, by prophylactic administration of the 5-adrenoblocker obzidan in the treatment with aminoglycoside antibiotics.

Deafness (deafness) is one of the most common complications of hearing loss in early childhood. With hearing loss in early childhood to 60 dB, the child's speech will become somewhat distorted, according to the degree of deafness. When hearing loss in a newborn child and in subsequent years at speech frequencies of more than 70 dB, a child with regard to speech learning can practically be identified with a completely deaf child. The development of such a child remains normal up to 1 year, after that a deaf child does not develop speech. He only says a few syllables, imitating the movements of his mother's lips. In 2-3 years the child does not speak, but he has a highly developed facial expression, there are disorders of the psyche and intellect. The child is closed, detached from other children, non-contact, quick-tempered and irritable. Less often children, on the contrary, are expansive, excessively hilarious and mobile; their attention is attracted by everything around them, but it is unstable and superficial. Children suffering from deaf mutes are subject to special accounting; in relation to them, it is necessary to carry out social and rehabilitation measures, provided for by special instructions and legislative acts, in special kindergartens and educational institutions in which surdopedagogical classes are conducted.

Surmedagogy is the science of educating and educating children with hearing impairments. The tasks of surdopedagogics are to overcome the consequences of hearing impairment, to develop ways to compensate them in the process of education and upbringing, and to form the child as a socially adequate subject of society. The most severe consequence of deafness and expressed hearing loss is the obstacle that they create for the normal development of speech, and sometimes the psyche of the child. The basic sciences for language education are linguistics, psychology, physiology and medicine that help to reveal the structure of the violation, the peculiarities of the mental and physical development of children with hearing impairments, the mechanism for compensating this violation and outline the ways of its implementation. A classification of hearing impairments in children has been created by domestic diploma education, which is the basis of the system of their differentiated education and training in special institutions for children of the nursery, preschool and school age. Surmedagogy is based on the general principles of training and education of deaf, deaf and deaf children of all ages. There are special curricula, programs, textbooks and manuals, as well as methodological guides for students and practitioners. Surmedagogy as a teaching discipline is taught at defectology faculties of pedagogical universities and at courses of advanced training of faculty.

In modern conditions of technical progress, audio and video-electronic means, including computer programming of electronic means of hearing rehabilitation, are gaining more and more importance for audio-pedagogy. Of great importance for this problem are the latest developments in computer audiometry, which is based on the method of registration and analysis of auditory evoked potentials. All new technical means are being developed, such as sound and hearing instruments, sound amplifying and sound analyzing apparatuses, apparatus for the transformation of audio speech into optical or tactile signals. Great importance in the social rehabilitation of the deaf people of all ages belongs to individual means of hearing correction, which form the basis of hearing care.

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