Abstract:
Recent studies have questioned the adequacy of current noise standards for intense impulses, especially those with large low-frequency content, a category which includes air bag deployments. Unfortunately, almost no tests have been done with real ears and air bag impulses. Such data are also needed for development of theory and validation of our hearing loss model [G. R. Price and J. T. Kalb, J. Acoust. Soc. Am. 90, 219--227 (1991)]. Therefore, 32 anesthetized cats positioned at the driver and passenger locations in a pickup truck were exposed in pairs to one air bag deployment (electrically initiated). Hearing was tested at 1, 2, 4, 8, and 16 kHz by evoked-response audiometry before exposure, immediately after, 1 month, and 6 months later. Exposure conditions included doors open, compartment closed, and closed compartment sealed with tape; seven exposures to passenger bag only and nine to driver and passenger bags. Pressures at inboard ears ranged from 167- to 173-dB peak and B durations from approximately 50--150 ms, with unweighted energies as high as 4000 J/m[sup 2] (or 8 h L[inf EQA]=95.5 dB). All ears showed significant hearing losses immediately, averaging 60-dB threshold shift at 4.0 kHz which resolved to an average PTS of 37 dB.