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Group tonal audiometry

I. Škarić ; Filozofski fakultet i Fakultet za defektologiju Sveučilišta u Zagrebu, Zagreb

Puni tekst: hrvatski pdf 5.791 Kb

str. 355-360

preuzimanja: 244



Systematic examinations of hearing are indispensable especially when the populations of school children and workers exposed to noise are concerned. The latter should undergo regular check-ups every three to six months at the beginning and later at least once a year. So far this has been the only reliable method of discovening excessive sensitivity to noise and protecting workers from noise before their hearing is considerably impaired. As such audio-logical check-ups are rather expensive they are undertaken for the time being only for demonstration and research sake and do not make part of a routine procedure. The existing group audiometry which is baked on signals-numbers is not very useful for such systematic check-ups; it has two shortcomings: a) it does not register small and partial defficiencies typical for the initial stage of a hearing impairment and b) it does not provide us with a tonal audiogram on which audiology has based its criteria for the interpretation of the hearing status. This was the reason why we made up a kind of group tonal audiometry. While experimenting with this new procedure we realized that it was as simple to carry out as it was sensitive and efficient. The time usually needed for individual audiometry is here shortened up to fifty times: the whole testing procedure lasts about 25 minutes and about SO people can be tested at a time. The equipment needed for this new audiometry is extremely simple: a tape-recorder, a test-tape and a test-form (Fig. 1). On the test-tape are recorded the same (pure tone) signals the routine tonal audiometry uses (250, 500, 1 000, 2 000, 4 000, 6 000, 8 000 cycles). Each of these tones is recorded at seven different intensity levels (50 dB above the threshold, 40 dB, 30 dB, 20 dB, 10 dB, 5 dB and O dB). The decision on the number of impulses (1, 2 or 3) in each item is left to chance. The examinee is supposed to draw as many lines on the paper as there are impulses he can perceive. In case he does not make any mark or draws the wrong number of lines it will mean that he did not hear (Fig. 1). Before each signal is heard the number corresponding to the numbers on the form will be announced. This kind of audiometry can be carried out in any room or hall (classroom, conference hall etc), the only condition being that the stationary noise level should not exceed 35 phons. The signals are perceived directly from the tape-recorder without earphones. After having listened to the whole of the 12 minute long test the examinees are given the correct answers. They will encircle the wrong answers and make a cross in the »Audiogram«. The audiogram obtained by linking together the crosses is more or less the same as the one obtained in individual testing. It can serve very well not only as a »screening« test but also as a final picture of the hearing status which is accurate enough to enable a longitudinal observation of the hearing status of workers exposed to noise.

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