Abstract
Eighteen guinea pigs received infrasound (1, 10, 20 Hz) at 120-163 dB SPL for one hour. The animals did not show any nystagmus and/or disturbance of balance during infrasound exposure. They were sacrificed fourteen days after the exposure. The temporal bones were examined light microscopically. Pathological findings were loss and degeneration of outer hair cells and globus formation on the under surface of the tectorial membrane in the apical turn of the cochlea. These morphological changes were noted in the ears exposed by 20 Hz at 163 dB SPL. The stria vascularis and the spiral ligament were normal in all ears examined. There were no atrophy of the spiral and vestibular ganglion cells and of the cochlear and vestibular nerves in all experimented animals. The saccule, the utricule and semicircular canals were normal in sectioned specimens. As frequency and intensity of the sound increased the number of ears with pathologies increased. It is concluded from the present light microscopic observation that one hour exposure of the infrasound below 140 dB SPL does not induce any morphological changes in the ear of the guinea pig.
