CUMULATIVE AUDITORY EFFECTS RESULTING FROM MULTIPLE EXPOSURE TO INTENSE ACOUSTIC STIMULATION PART Ⅱ. HISTOLOGICAL EFFECTS OF INTENSE SOUND ON THE INNER EAR

摘要

Thirty-three oats were subjected to sound exposures; and auditory threshold shift measurements are reported in Part I. The animals were subsequently sacrificed and their inner ears prepared for microscopic examination for evidence of tissue injury. The histological findings of injuries are reported in this report.nWide band noise at 115 db for one-half hour produced mild injuries; for 2-hour exposures the injuries were moderate to severe; for 8-hour exposures there were severe injuries. Post-exposure lives of these animals were 80 to 90 days. Animals sacrificed 2 to 4 hours after exposure showed essentially the same degree of injury with the same 2-hour exposure as above.nTwo hours total exposure at 115 db divided into 16 doses of 7.5 minutes each, with one hour inter-exposure intervals. resulted in slight to moderate changes. The same total energy in the same number of doses for 7.5 minutes, with an inter-exposure interval of 6 hours, produced comparatively slight injuries.nWhile considerable variability is evident in different specimens subjected to the same exposure for the same length of time, there persists a general trend for consistency of degree of injury in each group.