Abstract: Characteristics of hearing damage to guinea pigs caused by different compression rates were studied using morphological examination, measurement of auditory evoked potential, surface preparation technique and scanning electron microscopy. The results show that, at a lower compression rate pathological changes in tympanic cavity (TC) and round window (RW), damage to outer hair cell (OHC) of inner ear occurrs more frequently, along with vestibular dysfunction in some of the tested animals. At a higher compression rate, however, rupture of tympanic membrane (TM) is particularly liable to happen, with slight damage to TC, RW and OHC. Based on these results different mechanisms responsible for the damage are discussed. This study shows that severe hearing damage can occur at lower compression rates, although no rupture of TM is found.