Drill-generated noise levels in ear surgery.

The noise levels in the cochlea when a drill is used in the mastoid process have been calculated from vibration measurements on intact skulls of human cadavers and temporal bones. The results lend support to the conclusion that, in ear surgery the ipsilateral cochlea is exposed to noise levels of about 100 dB and the contralateral cochlea to levels 5-10 dB lower every time the drill is used. This noise trauma may account for some of the high-tone sensorineural hearing losses after tympanoplasty described by other authors.