Auditory Response to the Acoustic Impulse from an Air-Bag Crash Protection System

Abstract

The potential acoustic hazard of an impulsive noise generated inside an automobile by inflation of a rapidly expanding air-bag personal crash protection system was evaluated. Widespread use of this system in vehicles would result in an average exposure of about one impulse per person over a lifetime. The acoustic impulse is characterized by a median duration of 21 msec, median rise time of 5 msec and median peak pressure level of 168 dB. Ninety-one volunteers experienced the single intense impulse without ear protection and their pre- and postexposure audiometric and otologic examinations provided measures of auditory responses. Otologic effects on the drum membrane were negative. No discomfort or aural pain was reported. About 50% of the subjects and 35% of the ears experienced some temporary threshold shift with 65% of the ears recovering within 24 h. Many subjects reported short duration tinnitus. Results indicate that the impulsive noise is very loud; however, the probability of irreversible harm to the auditory systems of vehicle occupants may be considered to be extremely small.