From Big Medical Encyclopedia

HEARING AID — use of hearing aids for the purpose of improvement of hearing. The page is shown at the bilateral relative deafness or unilateral relative deafness and deafness on other ear complicating speech communication (see. Surdomutism , Relative deafness ), performance of professional duties, and also satisfaction of spiritual needs of the person.

Contraindications for S. are acoustical hyperesthesias, disorder of function of a vestibular analyzer, an acute inflammation of an outside or middle ear, a foreign body of outside acoustical pass, an aggravation hron. purulent average otitis, acute deafness or relative deafness within the first 3 months.

The correct selection is important for successful S. hearing aid (see). For this purpose, in addition to tone threshold audiometriya (see), carry out a speech audiometriya in a free sound field, measure thresholds of acoustical discomfort, investigate a noise stability of the acoustic analyzer, reveal existence dysfunction of loudness. The recommended type of the hearing aid is that, to-ry gives the lowest threshold of 50% of legibility of the speech, the greatest percent of legibility of the speech at her most comfortable perception, the greatest threshold of discomfort of perception of the speech and the smallest size of a ratio a signal noise.

The issue of binaural S., use of hearing aids with air or bone carrying out a sound and use of an ear insert is individually resolved. Monaural S. is carried out by pases to the party of the best legibility of the speech with a flat audiometric curve, the high threshold of discomfortable perception of the speech giving with the hearing aid big legibility of the speech at the most comfortable level of her perception. An essential role is played by a design of individual ear inserts.

At primary hearing aid the period of adaptation in different acoustic situations within about 1 month is necessary, after to-rogo necessary correction can be made to acoustic parameters of the hearing aid.

To S. children of early age are applied by the hearing aids having the maximum output level of sound pressure no more than 110 dB, nonlinear distortions less than 10% and own noise of the hearing aid no more than 30 dB. The frequency band of the hearing aid for the children who are not owning the speech is chosen the widest since training of the speech requires complete acoustic information about speech sounds. The frequency band of the hearing aid for adults can be limited to the limits sufficient for recognition of speech sounds.

Acoustic suitability of S. comes to light at selection of the hearing aid; the behavioural efficiency including psychological, household, professional and social factors comes to light in the course of use of the hearing aid. S.'s efficiency of children is determined by the characteristic of speech development, success of training.

The conclusion about S.'s expediency shall be drawn with participation of a surdopedagog. At the wrong selection of the hearing aid, its inept use or existence of S.'s failure in it can lead to deterioration in legibility of the speech.

See also Prosthetics , Hearing .

Bibliography: Preobrazhensky Yu. B. and Godin L. S. Bases of acoustical prosthetics of children. M, 1973, bibliogr.; M. M Efruss. Hearing aids and audiometers, M., 11*75, bibliogr.; With and-hart of R. Tests for selection of hearing * aids, Laryngoscope (St Louis), v. 56. p. 780, 1946; P a s with o e D. P. Frequency responses of hearing aids and their effects on the speech perception of hearing-impaired subjects, Ann. Otol. (St Louis), v. 84, suppl. 23, p. 1, 1975.

O. P. Tokarev.