Abstract
The purpose of this study is to investigate the influence of intense sound on static body balance. Thirty-three subjects and thirty subjects with auditory or vestibular disorders were examined in Romberg's posture on forceplate (gravicorder, Anima Co.). 500 Hz: 87, 107, 127 dB SPL pure tones were applied to each ears for 5 seconds from head phone and the body sways of center of gravity to the lateral directions for 10 seconds were summated 10 times by signal processor (NEC-sanei, 7 T-07 A).
The response pattern of normal subjects was classified into 3 types: type A (no remarkable body sway, 52%); type B (symmetrical body sway, 42%); type C (asymmetrical body sway, 6%). These results suggest that abnormal response pattern is the significant asymmetry or inversion of body sway in proportion to increasing of sound levels.
As for auditory findings, no specific correlations were observed between the response pattern of body sway and hearing impairment of subjects. One case of sudden deafness and two cases of perilymphatic fistula showed distinct abnormal responses, but no nystagmus was observed when the same stimuli were applied in each case. Two cases of Meniere's disease showed inversion of body sway in proportion to increasing of sound levels.
Parker and Reschke (1972) monitored perilymph pressure changes and stapes displacement related to acoustical stimulation in guinea pigs. They noted that intense sound made nonlinear stapes displacement and perilymph pressure change. This mechanism suggests the fact that on-off effect of 500 Hz acoustical stimulation may play analogous effects those of static pressure applied to the external auditory canal. And it may play part of the mechanisms of acoustical vestibular stimulation. It is concluded that this method may provide a new information about the certain pathological change of the vestibulue.
