AUDITORY FATIGUE EXAMINED BY BILATERAL LOUDNESS BALANCE TEST

KOBASHI Y.

doi:10.3950/jibiinkoka.62.1212

The behavior of the auditory fatigue can be divided into two groups: per-stimulatory and poststimulatory. In this paper per-stimulatory fatigue was determined by bilateral loudness balance test.During a continuous stimulation of 5 minutes at 90db sensation levels in 1000cps on one ear, a pure tone of short impulse in 1000cps was applied on the other ear 15 seconds and 30 seconds after the stimulation and thereafter every 30 seconds. By adjusting a balancing tone to a fatiguing tone, the loudness balance of sensation in both ears was obtained in every impulse.<br>In the testing of 100 persons with normal hearing, auditory fatigue developed abruptly in almost all individuals within first 15 seconds, and maintained a parallel equilibrium in 2 to 4 minutes at the dial ranging from 85 to 15db in the balancing ear. The distribution of the final level of balancing.tone seemed to correspond to the normal distribution with central peak around 60 to 45db. The auditory fatigue of the individual was always constant, and was not affected even by the condition of menstruation or general malaise, expect in cases of extremely severe physical fatigue such as playing mah-jong or heavy work through all the night.<br>The level shift of baeancing tone, namely the auditory fatigue, increased after the administration, of Priscol (1% Icc) in all 10 cases, and after Pilocarpin (1% 0.5cc) in 8 cases out of 10 cases, whereas decreased after the injection of Atropin (0.05% 1cc) in 5 cases out of 10 cases. The level was not affected by the injection of Nor-adrenalin (0.10 lcc). The auditory fatigue decreased following the intravenous injection of 7% sodium bicarbonate solution in 50cc dosis in 9 cases out of 12 cases.

AUDITORY FATIGUE EXAMINED BY BILATERAL LOUDNESS BALANCE TEST

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