[The acoustic trauma in animal experiment. II. Morphological reaction in the guinea pig cochlea after traumatisation by pure tones and octave band noise (a SEM- and TEM-study) (author's transl)].

Guinea pigs were exposed in groups to pure tones of varying frequences (1000, 3000, 5000 cps) and intensities in the range of 85--130 dB SPL. Other guinea pigs were exposed to octave band noise (180--5600 cps). By means of morphology we examined the immediate and late degenerative changes of the cochleae. The changes in sensory and supporting cells were simular after a short time overstimulation (130 db SPL--15 min) compared to a 5-days-stimulation at the 85 dB SPL level. After an OBN-Stimulation with 105 dB SPL--61 hours, lesions of sensory cells were found spread over several coils of the cochleae, with a predominance of the basal and 2nd coil. After pure tone stimulation the destruction of the organ of Corti was not tonotopically related according to the frequencies which were used in the experiments. The circumscribed destroyed areas in the organ of Corti were found mainly in the tonotopical range of the receptors of 2000--5000 cps--this means the end of the basal coil and the 2nd coil. The probable mere influence of direct mechanical stress is discussed.