| 摘 要： | Acoustic impedance changes and hearing threshold shifts after exposure to impulse noise or air-blasts were studied in guinea pigs.Air-blasts were produced by firing of live ammunition in a 100mm caliber gun,with peak SPL ranging from 172.9 to 190.3 dB for differnt groups of animals.Eachexposure consisted of 7—10 impulses.Blast impulses of the same origin were recorded on a tape re-corder and reproduced by playing back through loudspeaker system to serve as the source of impulsenoise.Each exposure consisted of 400 impulses,the peak SPL being 160 dB.Changes in tym-panograms of most animals after exposure to air-blasts suggested that hearing threshold shifts in thisgroup of animals were probably due to impairment of the middle ear.With respect to impulse noise,there was no evidance of severe damage to the middle ear although threshold shifts were obvious.Itwas proposed that inner ear trauma might be responsible for the latter changes.Cases with normal andabnormal tympanograms in the performed experiment we
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